Stop disabling force_compositing_mode for background RenderViews.

content/renderer/render_widget.cc

Index: content/renderer/render_widget.cc
diff --git a/content/renderer/render_widget.cc b/content/renderer/render_widget.cc
index 0f54094e7b18ec2711141658641f758a9c685586..b34edf07aee1ce40bfd39658d31c09cd4f4f2f6f 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -37,6 +37,7 @@
 #include "content/renderer/gpu/compositor_software_output_device.h"
 #include "content/renderer/gpu/delegated_compositor_output_surface.h"
 #include "content/renderer/gpu/mailbox_output_surface.h"
+#include "content/renderer/gpu/null_output_surface.h"
 #include "content/renderer/gpu/render_widget_compositor.h"
 #include "content/renderer/ime_event_guard.h"
 #include "content/renderer/input/input_handler_manager.h"
@@ -348,7 +349,8 @@ void RenderWidget::ScreenMetricsEmulator::OnShowContextMenu(
 RenderWidget::RenderWidget(blink::WebPopupType popup_type,
                            const blink::WebScreenInfo& screen_info,
                            bool swapped_out,
-                           bool hidden)
+                           bool hidden,
+                           bool background)
     : routing_id_(MSG_ROUTING_NONE),
       surface_id_(0),
       webwidget_(NULL),
@@ -365,6 +367,7 @@ RenderWidget::RenderWidget(blink::WebPopupType popup_type,
       num_swapbuffers_complete_pending_(0),
       did_show_(false),
       is_hidden_(hidden),
+      is_background_(background),
       is_fullscreen_(false),
       needs_repainting_on_restore_(false),
       has_focus_(false),
@@ -432,7 +435,7 @@ RenderWidget* RenderWidget::Create(int32 opener_id,
                                    const blink::WebScreenInfo& screen_info) {
   DCHECK(opener_id != MSG_ROUTING_NONE);
   scoped_refptr<RenderWidget> widget(
-      new RenderWidget(popup_type, screen_info, false, false));
+      new RenderWidget(popup_type, screen_info, false, false, false));
   if (widget->Init(opener_id)) {  // adds reference on success.
     return widget.get();
   }
@@ -880,6 +883,12 @@ bool RenderWidget::ForceCompositingModeEnabled() {
 }
 
 scoped_ptr<cc::OutputSurface> RenderWidget::CreateOutputSurface(bool fallback) {
+  if (is_background_) {
+    // Background RenderWidgets never produce visible output, so generate a
+    // NullOutputSurface that does nothing for them, and avoids allocating
+    // GPU contexts.
+    return scoped_ptr<cc::OutputSurface>(new NullOutputSurface());
+  }
 
 #if defined(OS_ANDROID)
   if (SynchronousCompositorFactory* factory =