diff --git a/browser/base/content/test/tabcrashed/browser.ini b/browser/base/content/test/tabcrashed/browser.ini
index 6542f241b95b..1266fb0564f0 100644
--- a/browser/base/content/test/tabcrashed/browser.ini
+++ b/browser/base/content/test/tabcrashed/browser.ini
@@ -5,12 +5,6 @@ support-files =
   file_contains_emptyiframe.html
   file_iframe.html
 
-[browser_aboutRestartRequired_basic.js]
-skip-if =
-  !debug
-[browser_aboutRestartRequired_buildid.js]
-skip-if =
-  !debug
 [browser_autoSubmitRequest.js]
 [browser_launchFail.js]
 [browser_multipleCrashedTabs.js]
diff --git a/browser/base/content/test/tabcrashed/browser_aboutRestartRequired.ini b/browser/base/content/test/tabcrashed/browser_aboutRestartRequired.ini
new file mode 100644
index 000000000000..f6f2cfea93ad
--- /dev/null
+++ b/browser/base/content/test/tabcrashed/browser_aboutRestartRequired.ini
@@ -0,0 +1,13 @@
+[DEFAULT]
+skip-if =
+  !debug || !e10s || !crashreporter
+support-files =
+  head.js
+prefs =
+  dom.ipc.processCount=1
+  dom.ipc.processPrelaunch.fission.number=0
+
+[browser_aboutRestartRequired_basic.js]
+[browser_aboutRestartRequired_buildid_false-positive.js]
+[browser_aboutRestartRequired_buildid_mismatch.js]
+[browser_aboutRestartRequired_buildid_no-platform-ini.js]
diff --git a/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_basic.js b/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_basic.js
index 34b4b284edd1..d62372cbba71 100644
--- a/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_basic.js
+++ b/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_basic.js
@@ -1,6 +1,11 @@
 "use strict";
 
-const kTimeout = 5 * 1000;
+// On debug builds, crashing tabs results in much thinking, which
+// slows down the test and results in intermittent test timeouts,
+// so we'll pump up the expected timeout for this test.
+requestLongerTimeout(5);
+
+SimpleTest.expectChildProcessCrash();
 
 add_task(async function test_browser_crashed_basic_event() {
   info("Waiting for oop-browser-crashed event.");
@@ -12,8 +17,9 @@ add_task(async function test_browser_crashed_basic_event() {
     "Build ID mismatch false positive count should be undefined"
   );
 
-  let eventPromise = getEventPromise("oop-browser-crashed", "basic", kTimeout);
-  await openNewTab(true);
+  await forceCleanProcesses();
+  let eventPromise = getEventPromise("oop-browser-crashed", "basic");
+  let tab = await openNewTab(true);
   await eventPromise;
 
   is(
@@ -21,4 +27,5 @@ add_task(async function test_browser_crashed_basic_event() {
     undefined,
     "Build ID mismatch false positive count should be undefined"
   );
+  await closeTab(tab);
 });
diff --git a/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_buildid.js b/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_buildid.js
deleted file mode 100644
index ff5deac703e2..000000000000
--- a/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_buildid.js
+++ /dev/null
@@ -1,184 +0,0 @@
-"use strict";
-
-const kTimeout = 60 * 1000;
-
-// On debug builds, crashing tabs results in much thinking, which
-// slows down the test and results in intermittent test timeouts,
-// so we'll pump up the expected timeout for this test.
-requestLongerTimeout(5);
-
-async function waitForObserver(topic) {
-  return new Promise(function(resolve, reject) {
-    info("Setting up observer for '" + topic + "'");
-    let interval = undefined;
-
-    let obs = {
-      observe() {
-        info("Observed '" + topic + "'");
-        clearInterval(interval);
-        Services.obs.removeObserver(obs, topic);
-        resolve();
-      },
-    };
-
-    Services.obs.addObserver(obs, topic);
-
-    let times = 0;
-    let intervalMs = 1000;
-    interval = setInterval(async () => {
-      info("Opening and closing tab '" + topic + "'");
-      await openNewTab(false);
-      times += intervalMs;
-      if (times > kTimeout) {
-        clearInterval(interval);
-        reject();
-      }
-    }, intervalMs);
-  });
-}
-
-async function forceCleanProcesses() {
-  const origPrefValue = SpecialPowers.getBoolPref(
-    "dom.ipc.processPrelaunch.enabled"
-  );
-  info(
-    "forceCleanProcesses: get dom.ipc.processPrelaunch.enabled=" + origPrefValue
-  );
-  await SpecialPowers.setBoolPref("dom.ipc.processPrelaunch.enabled", false);
-  info("forceCleanProcesses: set dom.ipc.processPrelaunch.enabled=false");
-  await SpecialPowers.setBoolPref(
-    "dom.ipc.processPrelaunch.enabled",
-    origPrefValue
-  );
-  info(
-    "forceCleanProcesses: set dom.ipc.processPrelaunch.enabled=" + origPrefValue
-  );
-  const currPrefValue = SpecialPowers.getBoolPref(
-    "dom.ipc.processPrelaunch.enabled"
-  );
-  ok(currPrefValue === origPrefValue, "processPrelaunch properly re-enabled");
-}
-
-add_task(async function test_browser_crashed_false_positive_event() {
-  info("Waiting for oop-browser-crashed event.");
-
-  Services.telemetry.clearScalars();
-  is(
-    getFalsePositiveTelemetry(),
-    undefined,
-    "Build ID mismatch false positive count should be undefined"
-  );
-
-  try {
-    setBuildidMatchDontSendEnv();
-    await forceCleanProcesses();
-    let eventPromise = getEventPromise(
-      "oop-browser-crashed",
-      "false-positive",
-      kTimeout
-    );
-    await openNewTab(false);
-    await eventPromise;
-  } finally {
-    unsetBuildidMatchDontSendEnv();
-  }
-
-  is(
-    getFalsePositiveTelemetry(),
-    1,
-    "Build ID mismatch false positive count should be 1"
-  );
-});
-
-add_task(async function test_browser_restartrequired_event() {
-  info("Waiting for oop-browser-buildid-mismatch event.");
-
-  Services.telemetry.clearScalars();
-  is(
-    getFalsePositiveTelemetry(),
-    undefined,
-    "Build ID mismatch false positive count should be undefined"
-  );
-
-  let profD = Services.dirsvc.get("GreD", Ci.nsIFile);
-  let platformIniOrig = await IOUtils.readUTF8(
-    PathUtils.join(profD.path, "platform.ini")
-  );
-  let buildID = Services.appinfo.platformBuildID;
-  let platformIniNew = platformIniOrig.replace(buildID, "1234");
-
-  await IOUtils.writeUTF8(
-    PathUtils.join(profD.path, "platform.ini"),
-    platformIniNew
-  );
-
-  try {
-    setBuildidMatchDontSendEnv();
-    await forceCleanProcesses();
-    let eventPromise = getEventPromise(
-      "oop-browser-buildid-mismatch",
-      "buildid-mismatch",
-      kTimeout
-    );
-    await openNewTab(false);
-
-    await eventPromise;
-  } finally {
-    await IOUtils.writeUTF8(
-      PathUtils.join(profD.path, "platform.ini"),
-      platformIniOrig
-    );
-
-    unsetBuildidMatchDontSendEnv();
-  }
-
-  is(
-    getFalsePositiveTelemetry(),
-    undefined,
-    "Build ID mismatch false positive count should be undefined"
-  );
-});
-
-add_task(async function test_browser_crashed_no_platform_ini_event() {
-  info("Waiting for oop-browser-buildid-mismatch event.");
-
-  Services.telemetry.clearScalars();
-  is(
-    getFalsePositiveTelemetry(),
-    undefined,
-    "Build ID mismatch false positive count should be undefined"
-  );
-
-  let profD = Services.dirsvc.get("GreD", Ci.nsIFile);
-  let platformIniOrig = await IOUtils.readUTF8(
-    PathUtils.join(profD.path, "platform.ini")
-  );
-
-  await IOUtils.remove(PathUtils.join(profD.path, "platform.ini"));
-
-  try {
-    setBuildidMatchDontSendEnv();
-    await forceCleanProcesses();
-    let eventPromise = getEventPromise(
-      "oop-browser-buildid-mismatch",
-      "no-platform-ini",
-      kTimeout
-    );
-    await openNewTab(false);
-
-    await eventPromise;
-  } finally {
-    await IOUtils.writeUTF8(
-      PathUtils.join(profD.path, "platform.ini"),
-      platformIniOrig
-    );
-
-    unsetBuildidMatchDontSendEnv();
-  }
-
-  is(
-    getFalsePositiveTelemetry(),
-    undefined,
-    "Build ID mismatch false positive count should be undefined"
-  );
-});
diff --git a/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_buildid_false-positive.js b/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_buildid_false-positive.js
new file mode 100644
index 000000000000..15e0b5ab312f
--- /dev/null
+++ b/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_buildid_false-positive.js
@@ -0,0 +1,35 @@
+"use strict";
+
+// On debug builds, crashing tabs results in much thinking, which
+// slows down the test and results in intermittent test timeouts,
+// so we'll pump up the expected timeout for this test.
+requestLongerTimeout(2);
+
+SimpleTest.expectChildProcessCrash();
+
+add_task(async function test_browser_crashed_false_positive_event() {
+  info("Waiting for oop-browser-crashed event.");
+
+  Services.telemetry.clearScalars();
+  is(
+    getFalsePositiveTelemetry(),
+    undefined,
+    "Build ID mismatch false positive count should be undefined"
+  );
+
+  ok(await ensureBuildID(), "System has correct platform.ini");
+  setBuildidMatchDontSendEnv();
+  await forceCleanProcesses();
+  let eventPromise = getEventPromise("oop-browser-crashed", "false-positive");
+  let tab = await openNewTab(false);
+  await eventPromise;
+  unsetBuildidMatchDontSendEnv();
+
+  is(
+    getFalsePositiveTelemetry(),
+    1,
+    "Build ID mismatch false positive count should be 1"
+  );
+
+  await closeTab(tab);
+});
diff --git a/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_buildid_mismatch.js b/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_buildid_mismatch.js
new file mode 100644
index 000000000000..80f35db159f6
--- /dev/null
+++ b/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_buildid_mismatch.js
@@ -0,0 +1,56 @@
+"use strict";
+
+// On debug builds, crashing tabs results in much thinking, which
+// slows down the test and results in intermittent test timeouts,
+// so we'll pump up the expected timeout for this test.
+requestLongerTimeout(2);
+
+SimpleTest.expectChildProcessCrash();
+
+add_task(async function test_browser_restartrequired_event() {
+  info("Waiting for oop-browser-buildid-mismatch event.");
+
+  Services.telemetry.clearScalars();
+  is(
+    getFalsePositiveTelemetry(),
+    undefined,
+    "Build ID mismatch false positive count should be undefined"
+  );
+
+  ok(await ensureBuildID(), "System has correct platform.ini");
+
+  let profD = Services.dirsvc.get("GreD", Ci.nsIFile);
+  let platformIniOrig = await IOUtils.readUTF8(
+    PathUtils.join(profD.path, "platform.ini")
+  );
+  let buildID = Services.appinfo.platformBuildID;
+  let platformIniNew = platformIniOrig.replace(buildID, "1234");
+
+  await IOUtils.writeUTF8(
+    PathUtils.join(profD.path, "platform.ini"),
+    platformIniNew,
+    { flush: true }
+  );
+
+  setBuildidMatchDontSendEnv();
+  await forceCleanProcesses();
+  let eventPromise = getEventPromise(
+    "oop-browser-buildid-mismatch",
+    "buildid-mismatch"
+  );
+  let tab = await openNewTab(false);
+  await eventPromise;
+  await IOUtils.writeUTF8(
+    PathUtils.join(profD.path, "platform.ini"),
+    platformIniOrig,
+    { flush: true }
+  );
+  unsetBuildidMatchDontSendEnv();
+
+  is(
+    getFalsePositiveTelemetry(),
+    undefined,
+    "Build ID mismatch false positive count should be undefined"
+  );
+  await closeTab(tab);
+});
diff --git a/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_buildid_no-platform-ini.js b/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_buildid_no-platform-ini.js
new file mode 100644
index 000000000000..232c79b02e83
--- /dev/null
+++ b/browser/base/content/test/tabcrashed/browser_aboutRestartRequired_buildid_no-platform-ini.js
@@ -0,0 +1,50 @@
+"use strict";
+
+// On debug builds, crashing tabs results in much thinking, which
+// slows down the test and results in intermittent test timeouts,
+// so we'll pump up the expected timeout for this test.
+requestLongerTimeout(2);
+
+SimpleTest.expectChildProcessCrash();
+
+add_task(async function test_browser_crashed_no_platform_ini_event() {
+  info("Waiting for oop-browser-buildid-mismatch event.");
+
+  Services.telemetry.clearScalars();
+  is(
+    getFalsePositiveTelemetry(),
+    undefined,
+    "Build ID mismatch false positive count should be undefined"
+  );
+
+  ok(await ensureBuildID(), "System has correct platform.ini");
+
+  let profD = Services.dirsvc.get("GreD", Ci.nsIFile);
+  let platformIniOrig = await IOUtils.readUTF8(
+    PathUtils.join(profD.path, "platform.ini")
+  );
+
+  await IOUtils.remove(PathUtils.join(profD.path, "platform.ini"));
+
+  setBuildidMatchDontSendEnv();
+  await forceCleanProcesses();
+  let eventPromise = getEventPromise(
+    "oop-browser-buildid-mismatch",
+    "no-platform-ini"
+  );
+  let tab = await openNewTab(false);
+  await eventPromise;
+  await IOUtils.writeUTF8(
+    PathUtils.join(profD.path, "platform.ini"),
+    platformIniOrig,
+    { flush: true }
+  );
+  unsetBuildidMatchDontSendEnv();
+
+  is(
+    getFalsePositiveTelemetry(),
+    undefined,
+    "Build ID mismatch false positive count should be undefined"
+  );
+  await closeTab(tab);
+});
diff --git a/browser/base/content/test/tabcrashed/head.js b/browser/base/content/test/tabcrashed/head.js
index 7f106d363f1d..552ad9ab30f0 100644
--- a/browser/base/content/test/tabcrashed/head.js
+++ b/browser/base/content/test/tabcrashed/head.js
@@ -146,42 +146,26 @@ function prepareNoDump() {
 }
 
 const kBuildidMatchEnv = "MOZ_BUILDID_MATCH_DONTSEND";
+const envService = Cc["@mozilla.org/process/environment;1"].getService(
+  Ci.nsIEnvironment
+);
 
 function setBuildidMatchDontSendEnv() {
-  const envService = Cc["@mozilla.org/process/environment;1"].getService(
-    Ci.nsIEnvironment
-  );
   info("Setting " + kBuildidMatchEnv + "=1");
   envService.set(kBuildidMatchEnv, "1");
-  info("Set " + kBuildidMatchEnv + "=1");
 }
 
 function unsetBuildidMatchDontSendEnv() {
-  const envService = Cc["@mozilla.org/process/environment;1"].getService(
-    Ci.nsIEnvironment
-  );
   info("Setting " + kBuildidMatchEnv + "=0");
   envService.set(kBuildidMatchEnv, "0");
-  info("Set " + kBuildidMatchEnv + "=0");
 }
 
-function getEventPromise(eventName, eventKind, kTimeout) {
+function getEventPromise(eventName, eventKind) {
   return new Promise(function(resolve, reject) {
-    /* eslint-disable mozilla/no-arbitrary-setTimeout */
-    let maybeTimeout = setTimeout(() => {
-      ok(
-        false,
-        "Timed out waiting " + eventName + " (" + eventKind + ") event"
-      );
-      reject();
-    }, kTimeout);
-
     info("Installing event listener (" + eventKind + ")");
     window.addEventListener(
       eventName,
       event => {
-        info("Clear timeout for " + eventKind + " event");
-        clearTimeout(maybeTimeout);
         ok(true, "Received " + eventName + " (" + eventKind + ") event");
         info("Call resolve() for " + eventKind + " event");
         resolve();
@@ -192,6 +176,15 @@ function getEventPromise(eventName, eventKind, kTimeout) {
   });
 }
 
+async function ensureBuildID() {
+  let profD = Services.dirsvc.get("GreD", Ci.nsIFile);
+  let platformIniOrig = await IOUtils.readUTF8(
+    PathUtils.join(profD.path, "platform.ini")
+  );
+  let buildID = Services.appinfo.platformBuildID;
+  return platformIniOrig.indexOf(buildID) > 0;
+}
+
 async function openNewTab(forceCrash) {
   const PAGE =
     "data:text/html,<html><body>A%20regular,%20everyday,%20normal%20page.";
@@ -205,14 +198,21 @@ async function openNewTab(forceCrash) {
   };
 
   let tab = await BrowserTestUtils.openNewForegroundTab(options);
-
   if (forceCrash === true) {
     let browser = tab.linkedBrowser;
-    await BrowserTestUtils.crashFrame(browser, true, true, null);
+    await BrowserTestUtils.crashFrame(
+      browser,
+      /* shouldShowTabCrashPage */ false,
+      /* shouldClearMinidumps */ true,
+      /* BrowsingContext */ null
+    );
   }
 
-  // Since we crashed early, we expect to have some about:blank
-  // Remove it to clean up
+  return tab;
+}
+
+async function closeTab(tab) {
+  await TestUtils.waitForTick();
   BrowserTestUtils.removeTab(tab);
 }
 
@@ -220,3 +220,24 @@ function getFalsePositiveTelemetry() {
   const scalars = TelemetryTestUtils.getProcessScalars("parent");
   return scalars["dom.contentprocess.buildID_mismatch_false_positive"];
 }
+
+// The logic bound to dom.ipc.processPrelaunch.enabled will react to value
+// changes: https://searchfox.org/mozilla-central/rev/ecd91b104714a8b2584a4c03175be50ccb3a7c67/dom/ipc/PreallocatedProcessManager.cpp#171-195
+// So we force flip to ensure we have no dangling process.
+async function forceCleanProcesses() {
+  const origPrefValue = SpecialPowers.getBoolPref(
+    "dom.ipc.processPrelaunch.enabled"
+  );
+  await SpecialPowers.setBoolPref(
+    "dom.ipc.processPrelaunch.enabled",
+    !origPrefValue
+  );
+  await SpecialPowers.setBoolPref(
+    "dom.ipc.processPrelaunch.enabled",
+    origPrefValue
+  );
+  const currPrefValue = SpecialPowers.getBoolPref(
+    "dom.ipc.processPrelaunch.enabled"
+  );
+  ok(currPrefValue === origPrefValue, "processPrelaunch properly re-enabled");
+}
diff --git a/browser/base/moz.build b/browser/base/moz.build
index 08025978748e..2d598b9a6e6b 100644
--- a/browser/base/moz.build
+++ b/browser/base/moz.build
@@ -56,6 +56,7 @@ BROWSER_CHROME_MANIFESTS += [
     "content/test/statuspanel/browser.ini",
     "content/test/sync/browser.ini",
     "content/test/tabcrashed/browser.ini",
+    "content/test/tabcrashed/browser_aboutRestartRequired.ini",
     "content/test/tabdialogs/browser.ini",
     "content/test/tabMediaIndicator/browser.ini",
     "content/test/tabPrompts/browser.ini",
diff --git a/ipc/glue/MessageChannel.cpp b/ipc/glue/MessageChannel.cpp
index 0ccd0ec6fe95..c8c1d5073459 100644
--- a/ipc/glue/MessageChannel.cpp
+++ b/ipc/glue/MessageChannel.cpp
@@ -873,8 +873,6 @@ bool MessageChannel::SendBuildIDsMatchMessage(const char* aParentBuildID) {
       // tooling to avoid intermittent missing leakcheck
       NoteIntentionalCrash(XRE_GetProcessTypeString());
       if (XRE_IsContentProcess()) {
-        // Make sure we do not die too early, as this causes weird behavior
-        PR_Sleep(PR_MillisecondsToInterval(1000));
         return false;
       }
     }