Add can-ignore-rect hint to clear call

src/gpu/gl/GrGpuGL.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "GrGpuGL.h"
 #include "GrGLStencilBuffer.h"
@@ skipping 1237 matching lines @@
             return;
         }
     }
     if (kNo_TriState != fHWScissorSettings.fEnabled) {
         GL_CALL(Disable(GR_GL_SCISSOR_TEST));
         fHWScissorSettings.fEnabled = kNo_TriState;
         return;
     }
 }
 
-void GrGpuGL::onClear(const SkIRect* rect, GrColor color) {
+void GrGpuGL::onClear(const SkIRect* rect, GrColor color, bool canIgnoreRect) {
     const GrDrawState& drawState = this->getDrawState();
     const GrRenderTarget* rt = drawState.getRenderTarget();
     // parent class should never let us get here with no RT
     SkASSERT(NULL != rt);
 
+    if (canIgnoreRect && this->glCaps().fullClearIsFree()) {
+        rect = NULL;
+    }
+
     SkIRect clippedRect;
     if (NULL != rect) {
         // flushScissor expects rect to be clipped to the target.
         clippedRect = *rect;
         SkIRect rtRect = SkIRect::MakeWH(rt->width(), rt->height());
         if (clippedRect.intersect(rtRect)) {
             rect = &clippedRect;
         } else {
             return;
         }
@@ skipping 1399 matching lines @@
             this->setVertexArrayID(gpu, 0);
         }
         int attrCount = gpu->glCaps().maxVertexAttributes();
         if (fDefaultVertexArrayAttribState.count() != attrCount) {
             fDefaultVertexArrayAttribState.resize(attrCount);
         }
         attribState = &fDefaultVertexArrayAttribState;
     }
     return attribState;
 }