Accelerate the lighten blendmode if GL_EXT_blend_minmax is enabled.

cc/output/gl_renderer.h

Index: cc/output/gl_renderer.h
diff --git a/cc/output/gl_renderer.h b/cc/output/gl_renderer.h
index 87739da440becb2d511d413a0bb586c407795c59..447f9ba1eda008825f5f0f2e7d0ca1a883655e58 100644
--- a/cc/output/gl_renderer.h
+++ b/cc/output/gl_renderer.h
@@ -143,9 +143,12 @@ class CC_EXPORT GLRenderer : public DirectRenderer {
                             const CheckerboardDrawQuad* quad);
   void DrawDebugBorderQuad(const DrawingFrame* frame,
                            const DebugBorderDrawQuad* quad);
-  static bool ShouldApplyBlendModeUsingBlendFunc(const DrawQuad* quad);
-  void ApplyBlendModeUsingBlendFunc(const DrawQuad* quad);
-  void RestoreBlendFuncToDefault();
+  static bool IsDefaultBlendMode(SkXfermode::Mode blend_mode) {
+    return blend_mode == SkXfermode::kSrcOver_Mode;
+  }
+  bool CanApplyBlendModeUsingBlendFunc(SkXfermode::Mode blend_mode);
+  void ApplyBlendModeUsingBlendFunc(SkXfermode::Mode blend_mode);
+  void RestoreBlendFuncToDefault(SkXfermode::Mode blend_mode);
   scoped_ptr<ScopedResource> GetBackgroundWithFilters(
       DrawingFrame* frame,
       const RenderPassDrawQuad* quad,
@@ -421,6 +424,7 @@ class CC_EXPORT GLRenderer : public DirectRenderer {
   ScopedPtrDeque<SyncQuery> available_sync_queries_;
   scoped_ptr<SyncQuery> current_sync_query_;
   bool use_sync_query_;
+  bool use_blend_minmax;
 
   SkBitmap on_demand_tile_raster_bitmap_;
   ResourceProvider::ResourceId on_demand_tile_raster_resource_id_;