Move some work from backend onClear to base class clear

src/gpu/GrImmediateDrawTarget.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrImmediateDrawTarget_DEFINED
 #define GrImmediateDrawTarget_DEFINED
 
@@ skipping 45 matching lines @@
                      const GrPathRange*,
                      const void* indices,
                      PathIndexType,
                      const float transformValues[],
                      PathTransformType,
                      int count,
                      const GrStencilSettings&,
                      const PipelineInfo&) override {
         SkFAIL("Only batch implemented\n");
     }
-    void onClear(const SkIRect* rect,
+    void onClear(const SkIRect& rect,
                  GrColor color,
-                 bool canIgnoreRect,
                  GrRenderTarget* renderTarget) override;
     void onCopySurface(GrSurface* dst,
                        GrSurface* src,
                        const SkIRect& srcRect,
                        const SkIPoint& dstPoint) override;
 
     bool isIssued(uint32_t drawID) override { return drawID != fDrawID; }
 
     bool SK_WARN_UNUSED_RESULT setupPipelineAndShouldDraw(void* pipelineAddr,
                                                           const GrDrawTarget::PipelineInfo&);
 
     void recordXferBarrierIfNecessary(const GrPipeline*);
 
     GrBatchTarget fBatchTarget;
     uint32_t fDrawID;
 
     typedef GrClipTarget INHERITED;
 };
 
 #endif