Delay creating DeferredGpuCommandService until gpu driver bug list is loaded.

DeferredGpuCommandService is created before gpu driver bug list is loaded,
so GpuDriverBugWorkarounds of DeferredGpuCommandService is empty in WebView.
In order to fix the bug, Delay creating DeferredGpuCommandService until
gpu driver bug list is loaded.

Change-Id: Ie594ad326cb1b3e6970efc007cfd6dfc4a826ebb
Reviewed-on: https://chromium-review.googlesource.com/597375
Commit-Queue: Bo Liu <boliu@chromium.org>
Reviewed-by: Bo Liu <boliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491709}

android_webview/browser/aw_browser_main_parts.cc

@@ -120,7 +120,6 @@ int AwBrowserMainParts::PreCreateThreads() {
 
   base::android::MemoryPressureListenerAndroid::RegisterSystemCallback(
       base::android::AttachCurrentThread());
-  DeferredGpuCommandService::SetInstance();
   breakpad::CrashDumpObserver::Create();
 
   if (crash_reporter::IsCrashReporterEnabled()) {
@@ -170,6 +169,10 @@ void AwBrowserMainParts::PreMainMessageLoopRun() {
 
   // TODO(meacer): Remove when PlzNavigate ships.
   content::RenderFrameHost::AllowDataUrlNavigationForAndroidWebView();
+
+  // This only works because webview uses in-process gpu
+  // which is not started up early by BrowserMainLoop.
+  DeferredGpuCommandService::SetInstance();
 }
 
 bool AwBrowserMainParts::MainMessageLoopRun(int* result_code) {