Move some work from backend onClear to base class clear

src/gpu/GrTargetCommands.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrTargetCommands.h"
 
 #include "GrBufferedDrawTarget.h"
@@ skipping 73 matching lines @@
 }
 
 void GrTargetCommands::DrawBatch::execute(GrGpu*) {
     fBatchTarget->flushNext(fBatch->numberOfDraws());
 }
 
 void GrTargetCommands::Clear::execute(GrGpu* gpu) {
     if (GrColor_ILLEGAL == fColor) {
         gpu->discard(this->renderTarget());
     } else {
-        gpu->clear(&fRect, fColor, fCanIgnoreRect, this->renderTarget());
+        gpu->clear(fRect, fColor, this->renderTarget());
     }
 }
 
 void GrTargetCommands::ClearStencilClip::execute(GrGpu* gpu) {
     gpu->clearStencilClip(fRect, fInsideClip, this->renderTarget());
 }
 
 void GrTargetCommands::CopySurface::execute(GrGpu* gpu) {
     gpu->copySurface(this->dst(), this->src(), fSrcRect, fDstPoint);
 }
 
 void GrTargetCommands::XferBarrier::execute(GrGpu* gpu) {
     gpu->xferBarrier(fRenderTarget.get(), fBarrierType);
 }