Revert of Revert of Move DstCopy on gpu into the GrXferProcessor.

src/gpu/gl/GrGLProgramDesc.cpp

Index: src/gpu/gl/GrGLProgramDesc.cpp
diff --git a/src/gpu/gl/GrGLProgramDesc.cpp b/src/gpu/gl/GrGLProgramDesc.cpp
index 32f831e84c8ca5a508c789da7ca75a67c966b4db..abe2439495d9cf35bb1283e0619b1d24bedd4e76 100644
--- a/src/gpu/gl/GrGLProgramDesc.cpp
+++ b/src/gpu/gl/GrGLProgramDesc.cpp
@@ -89,7 +89,6 @@
 bool GrGLProgramDescBuilder::Build(GrProgramDesc* desc,
                                    const GrPrimitiveProcessor& primProc,
                                    const GrPipeline& pipeline,
-                                   const GrProgramDesc::DescInfo& descInfo,
                                    const GrGLGpu* gpu,
                                    const GrBatchTracker& batchTracker) {
     // The descriptor is used as a cache key. Thus when a field of the
@@ -135,21 +134,7 @@
     // make sure any padding in the header is zeroed.
     memset(header, 0, kHeaderSize);
 
-    if (descInfo.fReadsDst) {
-        const GrDeviceCoordTexture* dstCopy = pipeline.getDstCopy();
-        SkASSERT(dstCopy || gpu->caps()->dstReadInShaderSupport());
-        const GrTexture* dstCopyTexture = NULL;
-        if (dstCopy) {
-            dstCopyTexture = dstCopy->texture();
-        }
-        header->fDstReadKey = GrGLFragmentShaderBuilder::KeyForDstRead(dstCopyTexture,
-                                                                       gpu->glCaps());
-        SkASSERT(0 != header->fDstReadKey);
-    } else {
-        header->fDstReadKey = 0;
-    }
-
-    if (descInfo.fReadsFragPosition) {
+    if (pipeline.readsFragPosition()) {
         header->fFragPosKey =
                 GrGLFragmentShaderBuilder::KeyForFragmentPosition(pipeline.getRenderTarget(),
                                                                   gpu->glCaps());