Revert of Move DstCopy on gpu into the GrXferProcessor.

src/gpu/gl/builders/GrGLFragmentShaderBuilder.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLFragmentShaderBuilder.h"
 #include "GrGLShaderStringBuilder.h"
 #include "GrGLProgramBuilder.h"
@@ skipping 161 matching lines @@
                          gpu->glCaps().fbFetchExtensionString());
 
         // Some versions of this extension string require declaring custom color output on ES 3.0+
         const char* fbFetchColorName = gpu->glCaps().fbFetchColorName();
         if (gpu->glCaps().fbFetchNeedsCustomOutput()) {
             this->enableCustomOutput();
             fOutputs[fCustomColorOutputIndex].setTypeModifier(GrShaderVar::kInOut_TypeModifier);
             fbFetchColorName = declared_color_output_name();
         }
         return fbFetchColorName;
+    } else if (fProgramBuilder->fUniformHandles.fDstCopySamplerUni.isValid()) {
+        return kDstCopyColorName;
     } else {
-        return kDstCopyColorName;
-    } 
+        return "";
+    }
+}
+
+void GrGLFragmentShaderBuilder::emitCodeToReadDstTexture() {
+    bool topDown = SkToBool(kTopLeftOrigin_DstReadKeyBit & fProgramBuilder->header().fDstReadKey);
+    const char* dstCopyTopLeftName;
+    const char* dstCopyCoordScaleName;
+    const char* dstCopySamplerName;
+    uint32_t configMask;
+    if (SkToBool(kUseAlphaConfig_DstReadKeyBit & fProgramBuilder->header().fDstReadKey)) {
+        configMask = kA_GrColorComponentFlag;
+    } else {
+        configMask = kRGBA_GrColorComponentFlags;
+    }
+    fProgramBuilder->fUniformHandles.fDstCopySamplerUni =
+            fProgramBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
+                                        kSampler2D_GrSLType,
+                                        kDefault_GrSLPrecision,
+                                        "DstCopySampler",
+                                        &dstCopySamplerName);
+    fProgramBuilder->fUniformHandles.fDstCopyTopLeftUni =
+            fProgramBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
+                                        kVec2f_GrSLType,
+                                        kDefault_GrSLPrecision,
+                                        "DstCopyUpperLeft",
+                                        &dstCopyTopLeftName);
+    fProgramBuilder->fUniformHandles.fDstCopyScaleUni =
+            fProgramBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
+                                        kVec2f_GrSLType,
+                                        kDefault_GrSLPrecision,
+                                        "DstCopyCoordScale",
+                                        &dstCopyCoordScaleName);
+    const char* fragPos = this->fragmentPosition();
+
+    this->codeAppend("// Read color from copy of the destination.\n");
+    this->codeAppendf("vec2 _dstTexCoord = (%s.xy - %s) * %s;",
+                      fragPos, dstCopyTopLeftName, dstCopyCoordScaleName);
+    if (!topDown) {
+        this->codeAppend("_dstTexCoord.y = 1.0 - _dstTexCoord.y;");
+    }
+    this->codeAppendf("vec4 %s = ", GrGLFragmentShaderBuilder::kDstCopyColorName);
+    this->appendTextureLookup(dstCopySamplerName,
+                              "_dstTexCoord",
+                              configMask,
+                              "rgba");
+    this->codeAppend(";");
 }
 
 void GrGLFragmentShaderBuilder::enableCustomOutput() {
     if (!fHasCustomColorOutput) {
         fHasCustomColorOutput = true;
         fCustomColorOutputIndex = fOutputs.count();
         fOutputs.push_back().set(kVec4f_GrSLType,
                                  GrGLShaderVar::kOut_TypeModifier,
                                  declared_color_output_name());
     }
@@ skipping 55 matching lines @@
     }
 }
 
 void GrGLFragmentShaderBuilder::addVarying(GrGLVarying* v, GrSLPrecision fsPrec) {
     v->fFsIn = v->fVsOut;
     if (v->fGsOut) {
         v->fFsIn = v->fGsOut;
     }
     fInputs.push_back().set(v->fType, GrGLShaderVar::kVaryingIn_TypeModifier, v->fFsIn, fsPrec);
 }