TrimMemory strategy while offscreenPreRaster is on.

android_webview/browser/shared_renderer_state.h

Index: android_webview/browser/shared_renderer_state.h
diff --git a/android_webview/browser/shared_renderer_state.h b/android_webview/browser/shared_renderer_state.h
index 3db14b7144114981f77f2fd0f8031ca768801daf..2224222a9c8fe6b79d8d46cddc34d97c82c41a8b 100644
--- a/android_webview/browser/shared_renderer_state.h
+++ b/android_webview/browser/shared_renderer_state.h
@@ -48,6 +48,7 @@ class SharedRendererState {
   void SwapReturnedResourcesOnUI(cc::ReturnedResourceArray* resources);
   bool ReturnedResourcesEmptyOnUI() const;
   scoped_ptr<ChildFrame> PassUncommittedFrameOnUI();
+  void DeleteHardwareRendererOnUI();
 
   // RT thread methods.
   gfx::Vector2d GetScrollOffsetOnRT();
@@ -78,6 +79,7 @@ class SharedRendererState {
   void UpdateParentDrawConstraintsOnUI();
   bool IsInsideHardwareRelease() const;
   void SetInsideHardwareRelease(bool inside);
+  void ReleaseCompositorResourcesIfNeededOnUI(bool release_hardware_draw);
 
   // Accessed by UI thread.
   scoped_refptr<base::SingleThreadTaskRunner> ui_loop_;