Add support for GL_*_shader_framebuffer_fetch

src/gpu/gl/GrGLProgramDesc.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLProgramDesc.h"
 #include "GrBackendEffectFactory.h"
 #include "GrDrawEffect.h"
@@ skipping 78 matching lines @@
             desc->fEffectKeys[s] = factory.glEffectKey(drawEffect, gpu->glCaps());
             if (effect->willReadDst()) {
                 readsDst = true;
             }
         } else {
             desc->fEffectKeys[s] = 0;
         }
     }
 
     if (readsDst) {
-        GrAssert(NULL != dstCopy);
-        desc->fDstRead = GrGLShaderBuilder::KeyForDstRead(dstCopy->texture(), gpu->glCaps());
+        GrAssert(NULL != dstCopy || gpu->caps()->dstReadInShaderSupport());
+        const GrTexture* dstCopyTexture = NULL;
+        if (NULL != dstCopy) {
+            dstCopyTexture = dstCopy->texture();
+        }
+        desc->fDstRead = GrGLShaderBuilder::KeyForDstRead(dstCopyTexture, gpu->glCaps());
         GrAssert(0 != desc->fDstRead);
     } else {
         desc->fDstRead = 0;
     }
 
     desc->fCoverageOutput = kModulate_CoverageOutput;
 
     // Currently the experimental GS will only work with triangle prims (and it doesn't do anything
     // other than pass through values from the VS to the FS anyway).
 #if GR_GL_EXPERIMENTAL_GS
@@ skipping 76 matching lines @@
 
     if (requiresCoverageAttrib) {
         desc->fCoverageAttributeIndex = drawState.coverageVertexAttributeIndex();
     } else if (GrGLProgramDesc::kAttribute_ColorInput == desc->fCoverageInput) {
         GrAssert(availableAttributeIndex < GrDrawState::kMaxVertexAttribCnt);
         desc->fCoverageAttributeIndex = availableAttributeIndex;
     } else {
         desc->fCoverageAttributeIndex = -1;
     }
 }