Cache the current WebPreferences on RenderViewHostImpl (try #2).

content/browser/renderer_host/render_view_host_impl.cc

Index: content/browser/renderer_host/render_view_host_impl.cc
diff --git a/content/browser/renderer_host/render_view_host_impl.cc b/content/browser/renderer_host/render_view_host_impl.cc
index b03d28fa685cafacbc1f1d2addf55f140067a5e5..b4280c58b671daa0c4f2781dd7f6e7ba3b9bca43 100644
--- a/content/browser/renderer_host/render_view_host_impl.cc
+++ b/content/browser/renderer_host/render_view_host_impl.cc
@@ -200,7 +200,8 @@ RenderViewHostImpl::RenderViewHostImpl(
       render_view_termination_status_(base::TERMINATION_STATUS_STILL_RUNNING),
       virtual_keyboard_requested_(false),
       weak_factory_(this),
-      is_focused_element_editable_(false) {
+      is_focused_element_editable_(false),
+      updating_web_preferences_(false) {
   DCHECK(instance_.get());
   CHECK(delegate_);  // http://crbug.com/82827
 
@@ -292,7 +293,7 @@ bool RenderViewHostImpl::CreateRenderView(
   ViewMsg_New_Params params;
   params.renderer_preferences =
       delegate_->GetRendererPrefs(GetProcess()->GetBrowserContext());
-  params.web_preferences = delegate_->GetWebkitPrefs();
+  params.web_preferences = GetWebkitPreferences();
   params.view_id = GetRoutingID();
   params.main_frame_routing_id = main_frame_routing_id_;
   params.surface_id = surface_id();
@@ -332,7 +333,7 @@ void RenderViewHostImpl::SyncRendererPrefs() {
                                         GetProcess()->GetBrowserContext())));
 }
 
-WebPreferences RenderViewHostImpl::GetWebkitPrefs(const GURL& url) {
+WebPreferences RenderViewHostImpl::ComputeWebkitPrefs(const GURL& url) {
   TRACE_EVENT0("browser", "RenderViewHostImpl::GetWebkitPrefs");
   WebPreferences prefs;
 
@@ -1423,7 +1424,10 @@ void RenderViewHostImpl::ExitFullscreen() {
 }
 
 WebPreferences RenderViewHostImpl::GetWebkitPreferences() {
-  return delegate_->GetWebkitPrefs();
+  if (!web_preferences_.get()) {
+    OnWebkitPreferencesChanged();
+  }
+  return *web_preferences_;
 }
 
 void RenderViewHostImpl::DisownOpener() {
@@ -1434,9 +1438,21 @@ void RenderViewHostImpl::DisownOpener() {
 }
 
 void RenderViewHostImpl::UpdateWebkitPreferences(const WebPreferences& prefs) {
+  web_preferences_.reset(new WebPreferences(prefs));
   Send(new ViewMsg_UpdateWebPreferences(GetRoutingID(), prefs));
 }
 
+void RenderViewHostImpl::OnWebkitPreferencesChanged() {
+  // This is defensive code to avoid infinite loops due to code run inside
+  // UpdateWebkitPreferences() accidentally updating more preferences and thus
+  // calling back into this code. See crbug.com/398751 for one past example.
+  if (updating_web_preferences_)
+    return;
+  updating_web_preferences_ = true;
+  UpdateWebkitPreferences(delegate_->ComputeWebkitPrefs());
+  updating_web_preferences_ = false;
+}
+
 void RenderViewHostImpl::GetAudioOutputControllers(
     const GetAudioOutputControllersCallback& callback) const {
   AudioRendererHost* audio_host =