Implement support for KHR_blend_equation_advanced

src/gpu/gl/builders/GrGLShaderBuilder.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 "GrGLShaderBuilder.h"
 #include "GrGLProgramBuilder.h"
 #include "GrGLShaderStringBuilder.h"
@@ skipping 155 matching lines @@
     append_texture_lookup(&this->code(),
                           fProgramBuilder->gpu(),
                           samplerName,
                           coordName,
                           configComponentMask,
                           swizzle,
                           kVec2f_GrSLType);
 }
 
 void GrGLShaderBuilder::addLayoutQualifier(const char* param, InterfaceQualifier interface) {
-    SkASSERT(fProgramBuilder->gpu()->glslGeneration() >= k330_GrGLSLGeneration);
+    SkASSERT(fProgramBuilder->gpu()->glslGeneration() >= k330_GrGLSLGeneration ||
+             fProgramBuilder->gpu()->glCaps().glslCaps()->mustEnableAdvBlendEqs());
     fLayoutParams[interface].push_back() = param;
 }
 
 void GrGLShaderBuilder::compileAndAppendLayoutQualifiers() {
     static const char* interfaceQualifierNames[] = {
         "out"
     };
 
     for (int interface = 0; interface <= kLastInterfaceQualifier; ++interface) {
         const SkTArray<SkString>& params = fLayoutParams[interface];
@@ skipping 34 matching lines @@
     fFinalized = true;
 
     if (!shaderId) {
         return false;
     }
 
     *shaderIds->append() = shaderId;
 
     return true;
 }