Use texture barriers to read directly from the RT

src/gpu/gl/GrGLGpu.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 "GrGLGpu.h"
 #include "GrGLStencilBuffer.h"
@@ skipping 2750 matching lines @@
             if(!SkIRect::IntersectsNoEmptyCheck(dstRect, srcRect)) {
                 return true;
             }
         } else {
             return true;
         }
     }
     return false;
 }
 
+void GrGLGpu::blendBarrier() {
+    // This shouldn't be called if there is coherent (or no) support for advanced blend equations.
+    SkASSERT(GrDrawTargetCaps::kAdvanced_BlendEquationSupport ==
+             this->caps()->blendEquationSupport());
+    GL_CALL(BlendBarrier());
+}
+
 void GrGLGpu::didAddGpuTraceMarker() {
     if (this->caps()->gpuTracingSupport()) {
         const GrTraceMarkerSet& markerArray = this->getActiveTraceMarkers();
         SkString markerString = markerArray.toStringLast();
 #if GR_FORCE_GPU_TRACE_DEBUGGING
         SkDebugf("%s\n", markerString.c_str());
 #else
         GL_CALL(PushGroupMarker(0, markerString.c_str()));
 #endif
     }
@@ skipping 35 matching lines @@
             this->setVertexArrayID(gpu, 0);
         }
         int attrCount = gpu->glCaps().maxVertexAttributes();
         if (fDefaultVertexArrayAttribState.count() != attrCount) {
             fDefaultVertexArrayAttribState.resize(attrCount);
         }
         attribState = &fDefaultVertexArrayAttribState;
     }
     return attribState;
 }