Add cap and builder feature for multisample interpolation

src/gpu/gl/GrGLCaps.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "GrGLCaps.h"
 
@@ skipping 622 matching lines @@
             ctxInfo.glslGeneration() >= k130_GrGLSLGeneration;
     } else {
         if (ctxInfo.hasExtension("GL_NV_shader_noperspective_interpolation")) {
             glslCaps->fNoPerspectiveInterpolationSupport = true;
             glslCaps->fNoPerspectiveInterpolationExtensionString =
                 "GL_NV_shader_noperspective_interpolation";
         }
     }
 
     if (kGL_GrGLStandard == standard) {
+        glslCaps->fMultisampleInterpolationSupport =
+                ctxInfo.glslGeneration() >= k400_GrGLSLGeneration;
+    } else {
+        if (ctxInfo.glslGeneration() >= k320es_GrGLSLGeneration) {
+            glslCaps->fMultisampleInterpolationSupport = true;
+        } else if (ctxInfo.hasExtension("GL_OES_shader_multisample_interpolation")) {
+            glslCaps->fMultisampleInterpolationSupport = true;
+            glslCaps->fMultisampleInterpolationExtensionString =
+                "GL_OES_shader_multisample_interpolation";
+        }
+    }
+
+    if (kGL_GrGLStandard == standard) {
         glslCaps->fSampleVariablesSupport = ctxInfo.glslGeneration() >= k400_GrGLSLGeneration;
     } else {
         if (ctxInfo.glslGeneration() >= k320es_GrGLSLGeneration) {
             glslCaps->fSampleVariablesSupport = true;
         } else if (ctxInfo.hasExtension("GL_OES_sample_variables")) {
             glslCaps->fSampleVariablesSupport = true;
             glslCaps->fSampleVariablesExtensionString = "GL_OES_sample_variables";
         }
     }
 
@@ skipping 1137 matching lines @@
         for (int j = 0; j < kExternalFormatUsageCnt; ++j) {
             SkASSERT(defaultEntry.fFormats.fExternalFormat[j] !=
                      fConfigTable[i].fFormats.fExternalFormat[j]);
         }
         SkASSERT(defaultEntry.fFormats.fExternalType != fConfigTable[i].fFormats.fExternalType);
     }
 #endif
 }
 
 void GrGLCaps::onApplyOptionsOverrides(const GrContextOptions& options) {}