Add can-ignore-rect hint to clear call

src/gpu/GrGpu.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGpu_DEFINED
 #define GrGpu_DEFINED
 
@@ skipping 247 matching lines @@
     /**
      * Remove resource from list of resources. Should only be called by
      * GrResource.
      * @param resource  the resource to remove.
      */
     void removeResource(GrResource* resource);
 
     // GrDrawTarget overrides
     virtual void clear(const SkIRect* rect,
                        GrColor color,
+                       bool canIgnoreRect,
                        GrRenderTarget* renderTarget = NULL) SK_OVERRIDE;
 
     virtual void purgeResources() SK_OVERRIDE {
         // The clip mask manager can rebuild all its clip masks so just
         // get rid of them all.
         fClipMaskManager.releaseResources();
     }
 
     // After the client interacts directly with the 3D context state the GrGpu
     // must resync its internal state and assumptions about 3D context state.
@@ skipping 141 matching lines @@
     virtual GrTexture* onCreateTexture(const GrTextureDesc& desc,
                                        const void* srcData,
                                        size_t rowBytes) = 0;
     virtual GrTexture* onWrapBackendTexture(const GrBackendTextureDesc&) = 0;
     virtual GrRenderTarget* onWrapBackendRenderTarget(const GrBackendRenderTargetDesc&) = 0;
     virtual GrVertexBuffer* onCreateVertexBuffer(size_t size, bool dynamic) = 0;
     virtual GrIndexBuffer* onCreateIndexBuffer(size_t size, bool dynamic) = 0;
     virtual GrPath* onCreatePath(const SkPath& path, const SkStrokeRec&) = 0;
 
     // overridden by backend-specific derived class to perform the clear and
-    // clearRect. NULL rect means clear whole target.
-    virtual void onClear(const SkIRect* rect, GrColor color) = 0;
+    // clearRect. NULL rect means clear whole target. If canIgnoreRect is
+    // true, it is okay to perform a full clear instead of a partial clear
+    virtual void onClear(const SkIRect* rect, GrColor color, bool canIgnoreRect) = 0;
 
     // overridden by backend-specific derived class to perform the draw call.
     virtual void onGpuDraw(const DrawInfo&) = 0;
 
     // overridden by backend-specific derived class to perform the path stenciling.
     virtual void onGpuStencilPath(const GrPath*, SkPath::FillType) = 0;
     virtual void onGpuDrawPath(const GrPath*, SkPath::FillType) = 0;
 
     // overridden by backend-specific derived class to perform flush
     virtual void onForceRenderTargetFlush() = 0;
@@ skipping 75 matching lines @@
     // these are mutable so they can be created on-demand
     mutable GrIndexBuffer*                                              fQuadIndexBuffer;
     // Used to abandon/release all resources created by this GrGpu. TODO: Move this
     // functionality to GrResourceCache.
     ResourceList                                                        fResourceList;
 
     typedef GrDrawTarget INHERITED;
 };
 
 #endif