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

src/gpu/gl/builders/GrGLProgramBuilder.cpp

Index: src/gpu/gl/builders/GrGLProgramBuilder.cpp
diff --git a/src/gpu/gl/builders/GrGLProgramBuilder.cpp b/src/gpu/gl/builders/GrGLProgramBuilder.cpp
index 088169622ccd3f397c2a185cd593bb75dcebcf7f..bb278be3953a5256c10f379785e7ccc4910adae5 100644
--- a/src/gpu/gl/builders/GrGLProgramBuilder.cpp
+++ b/src/gpu/gl/builders/GrGLProgramBuilder.cpp
@@ -55,12 +55,6 @@
     SkAutoTDelete<GrGLProgramBuilder> builder(CreateProgramBuilder(args, gpu));
 
     GrGLProgramBuilder* pb = builder.get();
-
-    // emit code to read the dst copy texture, if necessary
-    if (GrGLFragmentShaderBuilder::kNoDstRead_DstReadKey != pb->header().fDstReadKey &&
-        !gpu->glCaps().fbFetchSupport()) {
-        pb->fFS.emitCodeToReadDstTexture();
-    }
 
     // TODO: Once all stages can handle taking a float or vec4 and correctly handling them we can
     // seed correctly here