Bug 968604 Part 1: Fork the browser process from Nuwa. r=khuey

--HG--
extra : rebase_source : db94e3799dc8800b45e554fa07ef3f84a5cd5d78

dom/ipc/ContentChild.cpp

@@ -438,14 +438,22 @@ ContentChild::Init(MessageLoop* aIOLoop,
                                   XRE_GetProcessType());
 #endif
 
-    SendGetProcessAttributes(&mID, &mIsForApp, &mIsForBrowser);
-
     GetCPOWManager();
 
+    InitProcessAttributes();
+
+    return true;
+}
+
+void
+ContentChild::InitProcessAttributes()
+{
+    SendGetProcessAttributes(&mID, &mIsForApp, &mIsForBrowser);
+
 #ifdef MOZ_NUWA_PROCESS
     if (IsNuwaProcess()) {
         SetProcessName(NS_LITERAL_STRING("(Nuwa)"));
-        return true;
+        return;
     }
 #endif
     if (mIsForApp && !mIsForBrowser) {
@@ -454,7 +462,6 @@ ContentChild::Init(MessageLoop* aIOLoop,
         SetProcessName(NS_LITERAL_STRING("Browser"));
     }
 
-    return true;
 }
 
 void
@@ -794,6 +801,10 @@ ContentChild::RecvPBrowserConstructor(PBrowserChild* actor,
         MOZ_ASSERT(!sFirstIdleTask);
         sFirstIdleTask = NewRunnableFunction(FirstIdle);
         MessageLoop::current()->PostIdleTask(FROM_HERE, sFirstIdleTask);
+
+        // Redo InitProcessAttributes() when the app or browser is really
+        // launching so the attributes will be correct.
+        InitProcessAttributes();
     }
 
     return true;

dom/ipc/ContentChild.h

@@ -65,6 +65,7 @@ public:
     bool Init(MessageLoop* aIOLoop,
               base::ProcessHandle aParentHandle,
               IPC::Channel* aChannel);
+    void InitProcessAttributes();
     void InitXPCOM();
 
     static ContentChild* GetSingleton() {

dom/ipc/ContentParent.cpp

@@ -577,11 +577,24 @@ ContentParent::GetNewOrUsed(bool aForBrowserElement)
         return p.forget();
     }
 
-    nsRefPtr<ContentParent> p =
-        new ContentParent(/* app = */ nullptr,
-                          aForBrowserElement,
-                          /* isForPreallocated = */ false,
-                          PROCESS_PRIORITY_FOREGROUND);
+    // Try to take and transform the preallocated process into browser.
+    nsRefPtr<ContentParent> p = PreallocatedProcessManager::Take();
+    if (p) {
+        p->TransformPreallocatedIntoBrowser();
+    } else {
+      // Failed in using the preallocated process: fork from the chrome process.
+#ifdef MOZ_NUWA_PROCESS
+        if (Preferences::GetBool("dom.ipc.processPrelaunch.enabled", false)) {
+            // Wait until the Nuwa process forks a new process.
+            return nullptr;
+        }
+#endif
+        p = new ContentParent(/* app = */ nullptr,
+                              aForBrowserElement,
+                              /* isForPreallocated = */ false,
+                              PROCESS_PRIORITY_FOREGROUND);
+    }
+
     p->Init();
     sNonAppContentParents->AppendElement(p);
     return p.forget();
@@ -969,6 +982,14 @@ ContentParent::TransformPreallocatedIntoApp(const nsAString& aAppManifestURL)
     TryGetNameFromManifestURL(aAppManifestURL, mAppName);
 }
 
+void
+ContentParent::TransformPreallocatedIntoBrowser()
+{
+    // Reset mAppManifestURL, mIsForBrowser and mOSPrivileges for browser.
+    mAppManifestURL.Truncate();
+    mIsForBrowser = true;
+}
+
 void
 ContentParent::ShutDownProcess(bool aCloseWithError)
 {

dom/ipc/ContentParent.h

@@ -297,6 +297,10 @@ private:
     // process, for the specified manifest URL.
     void TransformPreallocatedIntoApp(const nsAString& aAppManifestURL);
 
+    // Transform a pre-allocated app process into a browser process. If this
+    // returns false, the child process has died.
+    void TransformPreallocatedIntoBrowser();
+
     /**
      * Mark this ContentParent as dead for the purposes of Get*().
      * This method is idempotent.