Bug 1558306 - Switch L10nRegistry initialization to happen right before the first content process gets created. r=mconley

Differential Revision: https://phabricator.services.mozilla.com/D34572

--HG--
extra : moz-landing-system : lando

browser/base/content/test/performance/browser_startup.js

@@ -35,8 +35,6 @@ const startupPhases = {
       "resource://gre/modules/MainProcessSingleton.jsm",
       "resource://gre/modules/XPCOMUtils.jsm",
       "resource://gre/modules/Services.jsm",
-      "resource://gre/modules/L10nRegistry.jsm",
-      "resource://gre/modules/Fluent.jsm",
       // Bugs to fix: The following components shouldn't be initialized that early.
       "resource://gre/modules/PushComponents.jsm", // bug 1369436
     ]),

dom/ipc/ContentParent.cpp

@@ -592,6 +592,9 @@ static bool sCanLaunchSubprocesses;
 // set.
 static bool sDisableUnsafeCPOWWarnings = false;
 
+// Set to true when the first content process gets created.
+static bool sCreatedFirstContentProcess = false;
+
 // The first content child has ID 1, so the chrome process can have ID 0.
 static uint64_t gContentChildID = 1;
 
@@ -2145,6 +2148,14 @@ void ContentParent::LaunchSubprocessInternal(
     AUTO_PROFILER_LABEL("ContentParent::LaunchSubprocess::resolve", OTHER);
     const auto launchResumeTS = TimeStamp::Now();
 
+    if (!sCreatedFirstContentProcess) {
+      nsCOMPtr<nsIObserverService> obs =
+          mozilla::services::GetObserverService();
+      obs->NotifyObservers(nullptr, "ipc:first-content-process-created",
+                           nullptr);
+      sCreatedFirstContentProcess = true;
+    }
+
     base::ProcessId procId = base::GetProcId(handle);
     Open(mSubprocess->GetChannel(), procId);
 #ifdef MOZ_CODE_COVERAGE

toolkit/components/processsingleton/MainProcessSingleton.jsm

@@ -55,10 +55,11 @@ MainProcessSingleton.prototype = {
   observe(subject, topic, data) {
     switch (topic) {
     case "app-startup": {
-      ChromeUtils.import("resource://gre/modules/CustomElementsListener.jsm", null);
-      ChromeUtils.import("resource://gre/modules/L10nRegistry.jsm");
+      Services.obs.addObserver(this, "ipc:first-content-process-created");
       Services.obs.addObserver(this, "xpcom-shutdown");
 
+      ChromeUtils.import("resource://gre/modules/CustomElementsListener.jsm", null);
+
       // Load this script early so that console.* is initialized
       // before other frame scripts.
       Services.mm.loadFrameScript("chrome://global/content/browser-content.js", true, true);
@@ -68,6 +69,14 @@ MainProcessSingleton.prototype = {
       break;
     }
 
+    case "ipc:first-content-process-created": {
+      // L10nRegistry needs to be initialized before any content
+      // process is loaded to populate the registered FileSource
+      // categories.
+      ChromeUtils.import("resource://gre/modules/L10nRegistry.jsm");
+      break;
+    }
+
     case "xpcom-shutdown":
       Services.mm.removeMessageListener("Search:AddEngine", this.addSearchEngine);
       break;