Move some work from backend onClear to base class clear

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 432 matching lines @@
     virtual GrTexture* onCreateCompressedTexture(const GrSurfaceDesc& desc,
                                                  GrGpuResource::LifeCycle lifeCycle,
                                                  const void* srcData) = 0;
     virtual GrTexture* onWrapBackendTexture(const GrBackendTextureDesc&, GrWrapOwnership) = 0;
     virtual GrRenderTarget* onWrapBackendRenderTarget(const GrBackendRenderTargetDesc&,
                                                       GrWrapOwnership) = 0;
     virtual GrVertexBuffer* onCreateVertexBuffer(size_t size, bool dynamic) = 0;
     virtual GrIndexBuffer* onCreateIndexBuffer(size_t size, bool dynamic) = 0;
 
     // overridden by backend-specific derived class to perform the clear.
-    virtual void onClear(GrRenderTarget*, const SkIRect* rect, GrColor color,
-                         bool canIgnoreRect) = 0;
+    virtual void onClear(GrRenderTarget*, const SkIRect* rect, GrColor color) = 0;
 
 
     // Overridden by backend specific classes to perform a clear of the stencil clip bits.  This is
     // ONLY used by the the clip target
     virtual void onClearStencilClip(GrRenderTarget*, const SkIRect& rect, bool insideClip) = 0;
 
     // overridden by backend-specific derived class to perform the draw call.
     virtual void onDraw(const DrawArgs&, const GrNonInstancedVertices&) = 0;
 
     virtual bool onGetReadPixelsInfo(GrSurface* srcSurface, int readWidth, int readHeight,
@@ skipping 53 matching lines @@
     GrTraceMarkerSet                                                    fActiveTraceMarkers;
     GrTraceMarkerSet                                                    fStoredTraceMarkers;
     // The context owns us, not vice-versa, so this ptr is not ref'ed by Gpu.
     GrContext*                                                          fContext;
 
     friend class GrPathRendering;
     typedef SkRefCnt INHERITED;
 };
 
 #endif