Workaround for blacklist KHR_blend_equation_advanced on ARM GPU

src/gpu/gl/GrGLGpu.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "GrGLGpu.h"
 #include "GrGLGLSL.h"
@@ skipping 2140 matching lines @@
     // tweaked the equation to "add" or "subtract", and the coeffs to (1, 0).
 
     GrBlendEquation equation = blendInfo.fEquation;
     GrBlendCoeff srcCoeff = blendInfo.fSrcBlend;
     GrBlendCoeff dstCoeff = blendInfo.fDstBlend;
     bool blendOff = (kAdd_GrBlendEquation == equation || kSubtract_GrBlendEquation == equation) &&
                     kOne_GrBlendCoeff == srcCoeff && kZero_GrBlendCoeff == dstCoeff;
     if (blendOff) {
         if (kNo_TriState != fHWBlendState.fEnabled) {
             GL_CALL(Disable(GR_GL_BLEND));
+
+            // Workaround for the ARM KHR_blend_equation_advanced blacklist issue
+            // https://code.google.com/p/skia/issues/detail?id=3943
+            if (kARM_GrGLVendor == this->ctxInfo().vendor() &&
+                GrBlendEquationIsAdvanced(fHWBlendState.fEquation)) {
+                SkASSERT(this->caps()->advancedBlendEquationSupport());
+                // Set to any basic blending equation.
+                GrBlendEquation blend_equation = kAdd_GrBlendEquation;
+                GL_CALL(BlendEquation(gXfermodeEquation2Blend[blend_equation]));
+                fHWBlendState.fEquation = blend_equation;
+            }
+
             fHWBlendState.fEnabled = kNo_TriState;
         }
         return;
     }
 
     if (kYes_TriState != fHWBlendState.fEnabled) {
         GL_CALL(Enable(GR_GL_BLEND));
         fHWBlendState.fEnabled = kYes_TriState;
     }
 
@@ skipping 935 matching lines @@
             this->setVertexArrayID(gpu, 0);
         }
         int attrCount = gpu->glCaps().maxVertexAttributes();
         if (fDefaultVertexArrayAttribState.count() != attrCount) {
             fDefaultVertexArrayAttribState.resize(attrCount);
         }
         attribState = &fDefaultVertexArrayAttribState;
     }
     return attribState;
 }