Bug 1341008 - Use the preallocated process manager by default. r=billm, r=kmag

To mitigate the delay that a new content process startup might cause, when the
browser reaches a non-busy state we attempt to prelaunch an empty content process
in the background that can be grabbed and used the next time we need one. This patch
enables the preallocated process manager by default and attempts to fix all the
issues that prevented us doing this sooner.

browser/app/profile/firefox.js

@@ -1573,6 +1573,8 @@ pref("browser.esedbreader.loglevel", "Error");
 
 pref("browser.laterrun.enabled", false);
 
+pref("dom.ipc.processPrelaunch.enabled", true);
+
 #ifdef EARLY_BETA_OR_EARLIER
 pref("browser.migrate.automigrate.enabled", true);
 #else

browser/base/content/test/social/browser_aboutHome_activation.js

@@ -82,7 +82,7 @@ function test() {
       info(testCase.desc);
 
       // Create a tab to run the test.
-      let tab = gBrowser.selectedTab = gBrowser.addTab("about:blank");
+      let tab = yield BrowserTestUtils.openNewForegroundTab(gBrowser);
 
       // Add an event handler to modify the snippets map once it's ready.
       let snippetsPromise = promiseSetupSnippetsMap(tab, testCase.snippet);
@@ -221,6 +221,6 @@ function activateProvider(tab, expectPanel, aCallback) {
 function waitForProviderLoad(cb) {
   return Promise.all([
     promiseObserverNotified("social:provider-enabled"),
-    ensureFrameLoaded(gBrowser, "https://example.com/browser/browser/base/content/test/social/social_postActivation.html"),
+    BrowserTestUtils.waitForNewTab(gBrowser, "https://example.com/browser/browser/base/content/test/social/social_postActivation.html"),
   ]);
 }

browser/extensions/formautofill/bootstrap.js

@@ -60,6 +60,9 @@ function startup() {
   Services.wm.addListener(windowListener);
 
   parent.init();
+  Services.ppmm.loadProcessScript("data:,new " + function() {
+    Components.utils.import("resource://formautofill/FormAutofillContent.jsm");
+  }, true);
   Services.mm.loadFrameScript("chrome://formautofill/content/FormAutofillFrameScript.js", true);
 }
 

dom/base/test/browser_messagemanager_loadprocessscript.js

@@ -49,6 +49,13 @@ function promiseMessage(messageManager, message) {
   })
 }
 
+add_task(function*(){
+  // We want to count processes in this test, so let's disable the pre-allocated process manager.
+  yield SpecialPowers.pushPrefEnv({"set": [
+    ["dom.ipc.processPrelaunch.enabled", false],
+  ]});
+})
+
 add_task(function*(){
   // This test is only relevant in e10s.
   if (!gMultiProcessBrowser)

dom/ipc/ContentParent.cpp

@@ -622,9 +622,6 @@ ContentParent::StartUp()
 
   BackgroundChild::Startup();
 
-  // Try to preallocate a process that we can use later.
-  PreallocatedProcessManager::AllocateAfterDelay();
-
   sDisableUnsafeCPOWWarnings = PR_GetEnv("DISABLE_UNSAFE_CPOW_WARNINGS");
 
 #if defined(XP_LINUX) && defined(MOZ_CONTENT_SANDBOX)

dom/ipc/PreallocatedProcessManager.cpp

@@ -110,6 +110,8 @@ PreallocatedProcessManagerImpl::Init()
                     /* weakRef = */ false);
     os->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID,
                     /* weakRef = */ false);
+    os->AddObserver(this, "profile-change-teardown",
+                    /* weakRef = */ false);
   }
   RereadPrefs();
 }
@@ -124,14 +126,18 @@ PreallocatedProcessManagerImpl::Observe(nsISupports* aSubject,
   } else if (!strcmp("nsPref:changed", aTopic)) {
     // The only other observer we registered was for our prefs.
     RereadPrefs();
-  } else if (!strcmp(NS_XPCOM_SHUTDOWN_OBSERVER_ID, aTopic)) {
+  } else if (!strcmp(NS_XPCOM_SHUTDOWN_OBSERVER_ID, aTopic) ||
+             !strcmp("profile-change-teardown", aTopic)) {
     Preferences::RemoveObserver(this, "dom.ipc.processPrelaunch.enabled");
     Preferences::RemoveObserver(this, "dom.ipc.processCount");
     nsCOMPtr<nsIObserverService> os = services::GetObserverService();
     if (os) {
       os->RemoveObserver(this, "ipc:content-shutdown");
       os->RemoveObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID);
+      os->RemoveObserver(this, "profile-change-teardown");
     }
+    mShutdown = true;
+    CloseProcess();
   } else {
     MOZ_ASSERT(false);
   }
@@ -142,7 +148,8 @@ PreallocatedProcessManagerImpl::Observe(nsISupports* aSubject,
 void
 PreallocatedProcessManagerImpl::RereadPrefs()
 {
-  if (Preferences::GetBool("dom.ipc.processPrelaunch.enabled")) {
+  if (mozilla::BrowserTabsRemoteAutostart() &&
+      Preferences::GetBool("dom.ipc.processPrelaunch.enabled")) {
     Enable();
   } else {
     Disable();
@@ -173,7 +180,7 @@ PreallocatedProcessManagerImpl::Enable()
 void
 PreallocatedProcessManagerImpl::AllocateAfterDelay()
 {
-  if (!mEnabled || mPreallocatedProcess) {
+  if (!mEnabled || mPreallocatedProcess || mShutdown) {
     return;
   }
 
@@ -189,7 +196,7 @@ PreallocatedProcessManagerImpl::AllocateAfterDelay()
 void
 PreallocatedProcessManagerImpl::AllocateOnIdle()
 {
-  if (!mEnabled || mPreallocatedProcess) {
+  if (!mEnabled || mPreallocatedProcess || mShutdown) {
     return;
   }
 
@@ -199,7 +206,7 @@ PreallocatedProcessManagerImpl::AllocateOnIdle()
 void
 PreallocatedProcessManagerImpl::AllocateNow()
 {
-  if (!mEnabled || mPreallocatedProcess ||
+  if (!mEnabled || mPreallocatedProcess || mShutdown ||
       ContentParent::IsMaxProcessCountReached(NS_LITERAL_STRING(DEFAULT_REMOTE_TYPE))) {
     return;
   }

layout/style/nsLayoutStylesheetCache.cpp

@@ -258,7 +258,7 @@ nsLayoutStylesheetCache::Shutdown()
   gCSSLoader_Servo = nullptr;
   gStyleCache_Gecko = nullptr;
   gStyleCache_Servo = nullptr;
-  MOZ_ASSERT(!gUserContentSheetURL, "Got the URL but never used?");
+  gUserContentSheetURL = nullptr;
 }
 
 void

toolkit/components/addoncompat/RemoteAddonsParent.jsm

@@ -1061,6 +1061,10 @@ var RemoteAddonsParent = {
 
     Services.ppmm.initialProcessData.remoteAddonsParentInitted = true;
 
+    Services.ppmm.loadProcessScript("data:,new " + function() {
+      Components.utils.import("resource://gre/modules/RemoteAddonsChild.jsm");
+    }, true);
+
     this.globalToBrowser = new WeakMap();
     this.browserToGlobal = new WeakMap();
   },

toolkit/components/extensions/Extension.jsm

@@ -1113,3 +1113,7 @@ this.Extension = class extends ExtensionData {
     return this._optionalOrigins;
   }
 };
+
+Services.ppmm.loadProcessScript("data:,new " + function() {
+  Components.utils.import("resource://gre/modules/ExtensionContent.jsm");
+}, true);