diff --git a/browser/components/extensions/test/browser/browser-common.ini b/browser/components/extensions/test/browser/browser-common.ini
index 1ae78777aba3..55e11d30d7af 100644
--- a/browser/components/extensions/test/browser/browser-common.ini
+++ b/browser/components/extensions/test/browser/browser-common.ini
@@ -60,7 +60,7 @@ skip-if = (debug && os == 'linux' && bits == 32) || (os == 'win' && !debug) # Bu
 [browser_ext_browserAction_popup_preload.js]
 skip-if = (os == 'win' && !debug) || (verify && debug && (os == 'mac')) # bug 1352668
 [browser_ext_browserAction_popup_resize.js]
-skip-if = (os == 'mac' && debug) # Bug 1482004, also fails in test-verify
+skip-if = (os == 'mac' || os == 'win' || os == 'linux') || (verify && debug) #Bug 1482004,1483701
 [browser_ext_browserAction_simple.js]
 [browser_ext_browserAction_telemetry.js]
 [browser_ext_browserAction_theme_icons.js]
diff --git a/devtools/client/debugger/new/test/mochitest/browser.ini b/devtools/client/debugger/new/test/mochitest/browser.ini
index 1bf51600fe1b..549ead677bfd 100644
--- a/devtools/client/debugger/new/test/mochitest/browser.ini
+++ b/devtools/client/debugger/new/test/mochitest/browser.ini
@@ -592,6 +592,7 @@ support-files =
   examples/fetch.js
   examples/doc-xhr.html
   examples/doc-xhr-run-to-completion.html
+  examples/doc-scroll-run-to-completion.html
   examples/sum/sum.js
   examples/sum/sum.min.js
   examples/sum/sum.min.js.map
@@ -650,6 +651,8 @@ support-files =
   examples/script-switching-02.js
   examples/script-switching-01.js
   examples/times2.js
+  examples/doc-windowless-workers.html
+  examples/simple-worker.js
   examples/doc_rr_basic.html
   examples/doc_rr_continuous.html
   examples/doc_rr_logs.html
@@ -662,6 +665,7 @@ support-files =
 skip-if = (os == "win" && ccov) # Bug 1453549
 [browser_dbg-xhr-breakpoints.js]
 [browser_dbg-xhr-run-to-completion.js]
+[browser_dbg-scroll-run-to-completion.js]
 [browser_dbg-sourcemapped-scopes.js]
 skip-if = ccov || (verify && debug && (os == 'linux')) # Bug 1441545
 [browser_dbg-sourcemapped-stepping.js]
@@ -762,6 +766,7 @@ skip-if = os == "win"
 skip-if = os == "win"
 [browser_dbg-wasm-sourcemaps.js]
 skip-if = true
+[browser_dbg-windowless-workers.js]
 [browser_dbg_rr_breakpoints-01.js]
 skip-if = os != "mac" || debug || !nightly_build
 [browser_dbg_rr_breakpoints-02.js]
diff --git a/devtools/client/debugger/new/test/mochitest/browser_dbg-scroll-run-to-completion.js b/devtools/client/debugger/new/test/mochitest/browser_dbg-scroll-run-to-completion.js
new file mode 100644
index 000000000000..b2128c489013
--- /dev/null
+++ b/devtools/client/debugger/new/test/mochitest/browser_dbg-scroll-run-to-completion.js
@@ -0,0 +1,19 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
+
+add_task(async function() {
+  const dbg = await initDebugger("doc-scroll-run-to-completion.html");
+  invokeInTab("pauseOnce", "doc-scroll-run-to-completion.html");
+  await waitForPaused(dbg);
+  assertPausedLocation(dbg);
+
+  const threadClient = dbg.toolbox.threadClient;
+  await checkEvaluateInTopFrame(threadClient, 'window.scrollBy(0, 10);', undefined);
+
+  // checkEvaluateInTopFrame does an implicit resume for some reason.
+  await waitForPaused(dbg);
+
+  resume(dbg);
+  await once(Services.ppmm, "test passed");
+});
diff --git a/devtools/client/debugger/new/test/mochitest/browser_dbg-windowless-workers.js b/devtools/client/debugger/new/test/mochitest/browser_dbg-windowless-workers.js
new file mode 100644
index 000000000000..5610a28a4b05
--- /dev/null
+++ b/devtools/client/debugger/new/test/mochitest/browser_dbg-windowless-workers.js
@@ -0,0 +1,45 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Test basic windowless worker functionality: the main thread and worker can be
+// separately controlled from the same debugger.
+add_task(async function() {
+  await pushPref("devtools.debugger.features.windowless-workers", true);
+
+  const dbg = await initDebugger("doc-windowless-workers.html");
+  const mainThread = dbg.toolbox.threadClient.actor;
+
+  const workers = await getWorkers(dbg);
+  ok(workers.length == 1, "Got one worker");
+  const workerThread = workers[0].actor;
+
+  const mainThreadSource = findSource(dbg, "doc-windowless-workers.html");
+  const workerSource = findSource(dbg, "simple-worker.js");
+
+  assertNotPaused(dbg);
+
+  await dbg.actions.breakOnNext();
+  await waitForPaused(dbg, "doc-windowless-workers.html");
+
+  // We should be paused at the timer in doc-windowless-workers.html
+  assertPausedAtSourceAndLine(dbg, mainThreadSource.id, 9);
+
+  await dbg.actions.selectThread(workerThread);
+  assertNotPaused(dbg);
+
+  await dbg.actions.breakOnNext();
+  await waitForPaused(dbg, "simple-worker.js");
+
+  // We should be paused at the timer in simple-worker.js
+  assertPausedAtSourceAndLine(dbg, workerSource.id, 3);
+
+  await stepOver(dbg);
+  assertPausedAtSourceAndLine(dbg, workerSource.id, 4);
+
+  await dbg.actions.selectThread(mainThread);
+
+  await stepOver(dbg);
+  assertPausedAtSourceAndLine(dbg, mainThreadSource.id, 10);
+});
diff --git a/devtools/client/debugger/new/test/mochitest/examples/doc-scroll-run-to-completion.html b/devtools/client/debugger/new/test/mochitest/examples/doc-scroll-run-to-completion.html
new file mode 100644
index 000000000000..6cc7f123ab78
--- /dev/null
+++ b/devtools/client/debugger/new/test/mochitest/examples/doc-scroll-run-to-completion.html
@@ -0,0 +1,27 @@
+ <!-- This Source Code Form is subject to the terms of the Mozilla Public
+    - License, v. 2.0. If a copy of the MPL was not distributed with this
+    - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<!DOCTYPE html>
+<meta charset=UTF-8>
+<body></body>
+<script>
+const cpmm = SpecialPowers.Services.cpmm;
+var result;
+
+for (var i = 0; i < 100; i++) {
+var div = document.createElement("div");
+div.innerHTML = "Hello World!";
+document.body.insertBefore(div, document.body.firstChild);
+}
+
+async function pauseOnce() {
+    window.addEventListener('scroll', done);
+    result = "test failed";
+    debugger;
+    result = "test passed";
+}
+
+function done() {
+    cpmm.sendAsyncMessage(result);
+}
+</script>
diff --git a/devtools/client/debugger/new/test/mochitest/examples/doc-windowless-workers.html b/devtools/client/debugger/new/test/mochitest/examples/doc-windowless-workers.html
new file mode 100644
index 000000000000..d745e9921e2a
--- /dev/null
+++ b/devtools/client/debugger/new/test/mochitest/examples/doc-windowless-workers.html
@@ -0,0 +1,19 @@
+<!DOCTYPE HTML>
+<html>
+
+<script>
+var worker = new Worker("simple-worker.js");
+
+var count = 0;
+function timer() {
+  var n = ++count;
+  console.log("MAIN THREAD SAYS HELLO! " + n);
+}
+
+setInterval(timer, 1000);
+</script>
+
+<body>
+Hello World!
+</body>
+</html>
diff --git a/devtools/client/debugger/new/test/mochitest/examples/simple-worker.js b/devtools/client/debugger/new/test/mochitest/examples/simple-worker.js
new file mode 100644
index 000000000000..b9c806fa8f88
--- /dev/null
+++ b/devtools/client/debugger/new/test/mochitest/examples/simple-worker.js
@@ -0,0 +1,7 @@
+var count = 0;
+function timer() {
+  var n = ++count;
+  console.log("WORKER SAYS HELLO! " + n);
+}
+
+setInterval(timer, 1000);
diff --git a/devtools/client/debugger/new/test/mochitest/helpers.js b/devtools/client/debugger/new/test/mochitest/helpers.js
index b9d37fd55dae..242eef122303 100644
--- a/devtools/client/debugger/new/test/mochitest/helpers.js
+++ b/devtools/client/debugger/new/test/mochitest/helpers.js
@@ -405,6 +405,34 @@ function isPaused(dbg) {
   return !!isPaused(getState());
 }
 
+// Make sure the debugger is paused at a certain source ID and line.
+function assertPausedAtSourceAndLine(dbg, expectedSourceId, expectedLine) {
+  assertPaused(dbg);
+
+  const {
+    selectors: { getWorkers, getFrames },
+    getState
+  } = dbg;
+
+  const frames = getFrames(getState());
+  ok(frames.length >= 1, "Got at least one frame");
+  const { sourceId, line } = frames[0].location;
+  ok(sourceId == expectedSourceId, "Frame has correct source");
+  ok(line == expectedLine, "Frame has correct line");
+}
+
+// Get any workers associated with the debugger.
+async function getWorkers(dbg) {
+  await dbg.actions.updateWorkers();
+
+  const {
+    selectors: { getWorkers },
+    getState
+  } = dbg;
+
+  return getWorkers(getState()).toJS();
+}
+
 async function waitForLoadedScopes(dbg) {
   const scopes = await waitForElement(dbg, "scopes");
   // Since scopes auto-expand, we can assume they are loaded when there is a tree node
diff --git a/devtools/client/webconsole/test/mochitest/browser.ini b/devtools/client/webconsole/test/mochitest/browser.ini
index d2fcb9780a79..c53fd2ef8bdc 100644
--- a/devtools/client/webconsole/test/mochitest/browser.ini
+++ b/devtools/client/webconsole/test/mochitest/browser.ini
@@ -168,7 +168,7 @@ support-files =
 skip-if = true # Bug 1437843
 [browser_console_consolejsm_output.js]
 [browser_console_context_menu_entries.js]
-skip-if = (os == "linux" && (debug || ccov)) # Bug 1440059
+skip-if = os == "linux" # Bug 1440059, disabled for all build types
 [browser_console_dead_objects.js]
 [browser_console_devtools_loader_exception.js]
 [browser_console_error_source_click.js]
diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index a4cb043e8a46..99dc5b3d08e9 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -8202,7 +8202,7 @@ bool nsContentUtils::IsThirdPartyWindowOrChannel(nsPIDOMWindowInner* aWindow,
   if (aWindow) {
     nsresult rv = thirdPartyUtil->IsThirdPartyWindow(aWindow->GetOuterWindow(),
                                                      aURI, &thirdParty);
-    if (NS_WARN_IF(NS_FAILED(rv))) {
+    if (NS_FAILED(rv)) {
       // Ideally we would do something similar to the channel code path here,
       // but existing code depends on this behaviour.
       return false;
diff --git a/dom/html/test/mochitest.ini b/dom/html/test/mochitest.ini
index 85f38785d7d0..b122e3045f5f 100644
--- a/dom/html/test/mochitest.ini
+++ b/dom/html/test/mochitest.ini
@@ -536,7 +536,7 @@ skip-if = toolkit == 'android' #bug 811644
 [test_bug340017.xhtml]
 [test_bug359657.html]
 [test_bug369370.html]
-skip-if = toolkit == "android" || toolkit == "windows" # disabled on Windows because of bug 1234520
+skip-if = toolkit == "android" || toolkit == "windows" || os == 'linux' # disabled on Windows because of bug 1234520, disabled on linux bug 1258103
 [test_bug380383.html]
 [test_bug402680.html]
 [test_bug403868.html]
diff --git a/dom/smil/nsSMILFloatType.cpp b/dom/smil/SMILFloatType.cpp
similarity index 65%
rename from dom/smil/nsSMILFloatType.cpp
rename to dom/smil/SMILFloatType.cpp
index 78ba493aeb0e..46753d6acee4 100644
--- a/dom/smil/nsSMILFloatType.cpp
+++ b/dom/smil/SMILFloatType.cpp
@@ -4,51 +4,52 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#include "nsSMILFloatType.h"
+#include "SMILFloatType.h"
 #include "nsSMILValue.h"
 #include "nsDebug.h"
 #include <math.h>
 
-void nsSMILFloatType::Init(nsSMILValue& aValue) const {
+namespace mozilla {
+
+void SMILFloatType::Init(nsSMILValue& aValue) const {
   MOZ_ASSERT(aValue.IsNull(), "Unexpected value type");
   aValue.mU.mDouble = 0.0;
   aValue.mType = this;
 }
 
-void nsSMILFloatType::Destroy(nsSMILValue& aValue) const {
+void SMILFloatType::Destroy(nsSMILValue& aValue) const {
   MOZ_ASSERT(aValue.mType == this, "Unexpected SMIL value");
   aValue.mU.mDouble = 0.0;
   aValue.mType = nsSMILNullType::Singleton();
 }
 
-nsresult nsSMILFloatType::Assign(nsSMILValue& aDest,
-                                 const nsSMILValue& aSrc) const {
+nsresult SMILFloatType::Assign(nsSMILValue& aDest,
+                               const nsSMILValue& aSrc) const {
   MOZ_ASSERT(aDest.mType == aSrc.mType, "Incompatible SMIL types");
   MOZ_ASSERT(aDest.mType == this, "Unexpected SMIL value");
   aDest.mU.mDouble = aSrc.mU.mDouble;
   return NS_OK;
 }
 
-bool nsSMILFloatType::IsEqual(const nsSMILValue& aLeft,
-                              const nsSMILValue& aRight) const {
+bool SMILFloatType::IsEqual(const nsSMILValue& aLeft,
+                            const nsSMILValue& aRight) const {
   MOZ_ASSERT(aLeft.mType == aRight.mType, "Incompatible SMIL types");
   MOZ_ASSERT(aLeft.mType == this, "Unexpected type for SMIL value");
 
   return aLeft.mU.mDouble == aRight.mU.mDouble;
 }
 
-nsresult nsSMILFloatType::Add(nsSMILValue& aDest,
-                              const nsSMILValue& aValueToAdd,
-                              uint32_t aCount) const {
+nsresult SMILFloatType::Add(nsSMILValue& aDest, const nsSMILValue& aValueToAdd,
+                            uint32_t aCount) const {
   MOZ_ASSERT(aValueToAdd.mType == aDest.mType, "Trying to add invalid types");
   MOZ_ASSERT(aValueToAdd.mType == this, "Unexpected source type");
   aDest.mU.mDouble += aValueToAdd.mU.mDouble * aCount;
   return NS_OK;
 }
 
-nsresult nsSMILFloatType::ComputeDistance(const nsSMILValue& aFrom,
-                                          const nsSMILValue& aTo,
-                                          double& aDistance) const {
+nsresult SMILFloatType::ComputeDistance(const nsSMILValue& aFrom,
+                                        const nsSMILValue& aTo,
+                                        double& aDistance) const {
   MOZ_ASSERT(aFrom.mType == aTo.mType, "Trying to compare different types");
   MOZ_ASSERT(aFrom.mType == this, "Unexpected source type");
 
@@ -60,10 +61,10 @@ nsresult nsSMILFloatType::ComputeDistance(const nsSMILValue& aFrom,
   return NS_OK;
 }
 
-nsresult nsSMILFloatType::Interpolate(const nsSMILValue& aStartVal,
-                                      const nsSMILValue& aEndVal,
-                                      double aUnitDistance,
-                                      nsSMILValue& aResult) const {
+nsresult SMILFloatType::Interpolate(const nsSMILValue& aStartVal,
+                                    const nsSMILValue& aEndVal,
+                                    double aUnitDistance,
+                                    nsSMILValue& aResult) const {
   MOZ_ASSERT(aStartVal.mType == aEndVal.mType,
              "Trying to interpolate different types");
   MOZ_ASSERT(aStartVal.mType == this, "Unexpected types for interpolation");
@@ -76,3 +77,5 @@ nsresult nsSMILFloatType::Interpolate(const nsSMILValue& aStartVal,
 
   return NS_OK;
 }
+
+}  // namespace mozilla
diff --git a/dom/smil/nsSMILFloatType.h b/dom/smil/SMILFloatType.h
similarity index 89%
rename from dom/smil/nsSMILFloatType.h
rename to dom/smil/SMILFloatType.h
index 8236fafaedf5..eaaceedb722e 100644
--- a/dom/smil/nsSMILFloatType.h
+++ b/dom/smil/SMILFloatType.h
@@ -10,11 +10,13 @@
 #include "mozilla/Attributes.h"
 #include "nsISMILType.h"
 
-class nsSMILFloatType : public nsISMILType {
+namespace mozilla {
+
+class SMILFloatType : public nsISMILType {
  public:
   // Singleton for nsSMILValue objects to hold onto.
-  static nsSMILFloatType* Singleton() {
-    static nsSMILFloatType sSingleton;
+  static SMILFloatType* Singleton() {
+    static SMILFloatType sSingleton;
     return &sSingleton;
   }
 
@@ -38,7 +40,9 @@ class nsSMILFloatType : public nsISMILType {
 
  private:
   // Private constructor: prevent instances beyond my singleton.
-  constexpr nsSMILFloatType() {}
+  constexpr SMILFloatType() {}
 };
 
+}  // namespace mozilla
+
 #endif  // NS_SMILFLOATTYPE_H_
diff --git a/dom/smil/moz.build b/dom/smil/moz.build
index 821bd41ccffd..27848682ccf0 100644
--- a/dom/smil/moz.build
+++ b/dom/smil/moz.build
@@ -44,7 +44,6 @@ UNIFIED_SOURCES += [
     'nsSMILCompositor.cpp',
     'nsSMILCSSProperty.cpp',
     'nsSMILCSSValueType.cpp',
-    'nsSMILFloatType.cpp',
     'nsSMILInstanceTime.cpp',
     'nsSMILInterval.cpp',
     'nsSMILKeySpline.cpp',
@@ -59,6 +58,7 @@ UNIFIED_SOURCES += [
     'nsSMILValue.cpp',
     'SMILBoolType.cpp',
     'SMILEnumType.cpp',
+    'SMILFloatType.cpp',
     'SMILIntegerType.cpp',
     'SMILStringType.cpp',
     'TimeEvent.cpp',
diff --git a/dom/svg/nsSVGLength2.cpp b/dom/svg/nsSVGLength2.cpp
index 3dc9fa9aabf6..68d474ad16bf 100644
--- a/dom/svg/nsSVGLength2.cpp
+++ b/dom/svg/nsSVGLength2.cpp
@@ -11,7 +11,7 @@
 #include "mozilla/dom/SVGViewportElement.h"
 #include "nsContentUtils.h"  // NS_ENSURE_FINITE
 #include "nsIFrame.h"
-#include "nsSMILFloatType.h"
+#include "SMILFloatType.h"
 #include "nsSMILValue.h"
 #include "nsSVGAttrTearoffTable.h"
 #include "nsSVGIntegrationUtils.h"
@@ -436,7 +436,7 @@ nsresult nsSVGLength2::SMILLength::ValueFromString(
     return NS_ERROR_DOM_SYNTAX_ERR;
   }
 
-  nsSMILValue val(nsSMILFloatType::Singleton());
+  nsSMILValue val(SMILFloatType::Singleton());
   val.mU.mDouble = value * mVal->GetPixelsPerUnit(mSVGElement, unitType);
   aValue = val;
   aPreventCachingOfSandwich =
@@ -448,7 +448,7 @@ nsresult nsSVGLength2::SMILLength::ValueFromString(
 }
 
 nsSMILValue nsSVGLength2::SMILLength::GetBaseValue() const {
-  nsSMILValue val(nsSMILFloatType::Singleton());
+  nsSMILValue val(SMILFloatType::Singleton());
   val.mU.mDouble = mVal->GetBaseValue(mSVGElement);
   return val;
 }
@@ -462,9 +462,9 @@ void nsSVGLength2::SMILLength::ClearAnimValue() {
 }
 
 nsresult nsSVGLength2::SMILLength::SetAnimValue(const nsSMILValue& aValue) {
-  NS_ASSERTION(aValue.mType == nsSMILFloatType::Singleton(),
+  NS_ASSERTION(aValue.mType == SMILFloatType::Singleton(),
                "Unexpected type to assign animated value");
-  if (aValue.mType == nsSMILFloatType::Singleton()) {
+  if (aValue.mType == SMILFloatType::Singleton()) {
     return mVal->SetAnimValue(float(aValue.mU.mDouble), mSVGElement);
   }
   return NS_OK;
diff --git a/dom/svg/nsSVGNumber2.cpp b/dom/svg/nsSVGNumber2.cpp
index 9af2c27c40a9..0abeb6a1d9c1 100644
--- a/dom/svg/nsSVGNumber2.cpp
+++ b/dom/svg/nsSVGNumber2.cpp
@@ -7,7 +7,7 @@
 #include "nsSVGNumber2.h"
 #include "mozilla/Attributes.h"
 #include "nsContentUtils.h"  // NS_ENSURE_FINITE
-#include "nsSMILFloatType.h"
+#include "SMILFloatType.h"
 #include "nsSMILValue.h"
 #include "nsSVGAttrTearoffTable.h"
 #include "SVGContentUtils.h"
@@ -126,7 +126,7 @@ nsresult nsSVGNumber2::SMILNumber::ValueFromString(
     return NS_ERROR_DOM_SYNTAX_ERR;
   }
 
-  nsSMILValue val(nsSMILFloatType::Singleton());
+  nsSMILValue val(SMILFloatType::Singleton());
   val.mU.mDouble = value;
   aValue = val;
   aPreventCachingOfSandwich = false;
@@ -135,7 +135,7 @@ nsresult nsSVGNumber2::SMILNumber::ValueFromString(
 }
 
 nsSMILValue nsSVGNumber2::SMILNumber::GetBaseValue() const {
-  nsSMILValue val(nsSMILFloatType::Singleton());
+  nsSMILValue val(SMILFloatType::Singleton());
   val.mU.mDouble = mVal->mBaseVal;
   return val;
 }
@@ -149,9 +149,9 @@ void nsSVGNumber2::SMILNumber::ClearAnimValue() {
 }
 
 nsresult nsSVGNumber2::SMILNumber::SetAnimValue(const nsSMILValue& aValue) {
-  NS_ASSERTION(aValue.mType == nsSMILFloatType::Singleton(),
+  NS_ASSERTION(aValue.mType == SMILFloatType::Singleton(),
                "Unexpected type to assign animated value");
-  if (aValue.mType == nsSMILFloatType::Singleton()) {
+  if (aValue.mType == SMILFloatType::Singleton()) {
     mVal->SetAnimValue(float(aValue.mU.mDouble), mSVGElement);
   }
   return NS_OK;