Add some backend flexibility for shader declarations in ProgramBuilding.

src/gpu/glsl/GrGLSLFragmentShaderBuilder.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 "GrGLSLFragmentShaderBuilder.h"
 #include "GrRenderTarget.h"
 #include "gl/GrGLGpu.h"
@@ skipping 198 matching lines @@
     }
 }
 
 void GrGLSLFragmentShaderBuilder::enableCustomOutput() {
     if (!fHasCustomColorOutput) {
         fHasCustomColorOutput = true;
         fCustomColorOutputIndex = fOutputs.count();
         fOutputs.push_back().set(kVec4f_GrSLType,
                                  GrGLSLShaderVar::kOut_TypeModifier,
                                  DeclaredColorOutputName());
+        fProgramBuilder->finalizeFragmentOutputColor(fOutputs.back());
     }
 }
 
 void GrGLSLFragmentShaderBuilder::enableSecondaryOutput() {
     SkASSERT(!fHasSecondaryOutput);
     fHasSecondaryOutput = true;
     const GrGLSLCaps& caps = *fProgramBuilder->glslCaps();
     if (const char* extension = caps.secondaryOutputExtensionString()) {
         this->addFeature(1 << kBlendFuncExtended_GLSLPrivateFeature, extension);
     }
 
     // If the primary output is declared, we must declare also the secondary output
     // and vice versa, since it is not allowed to use a built-in gl_FragColor and a custom
     // output. The condition also co-incides with the condition in whici GLES SL 2.0
     // requires the built-in gl_SecondaryFragColorEXT, where as 3.0 requires a custom output.
     if (caps.mustDeclareFragmentShaderOutput()) {
         fOutputs.push_back().set(kVec4f_GrSLType, GrGLSLShaderVar::kOut_TypeModifier,
                                  DeclaredSecondaryColorOutputName());
+        fProgramBuilder->finalizeFragmentSecondaryColor(fOutputs.back());
     }
 }
 
 const char* GrGLSLFragmentShaderBuilder::getPrimaryColorOutputName() const {
     return fHasCustomColorOutput ? DeclaredColorOutputName() : "gl_FragColor";
 }
 
 void GrGLSLFragmentBuilder::declAppendf(const char* fmt, ...) {
     va_list argp;
     va_start(argp, fmt);
@@ skipping 23 matching lines @@
 }
 
 void GrGLSLFragmentBuilder::onAfterChildProcEmitCode() {
     SkASSERT(fSubstageIndices.count() >= 2);
     fSubstageIndices.pop_back();
     fSubstageIndices.back()++;
     int removeAt = fMangleString.findLastOf('_');
     fMangleString.remove(removeAt, fMangleString.size() - removeAt);
 }