Add cap and builder feature for multisample interpolation

src/gpu/glsl/GrGLSLCaps.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef GrGLSLCaps_DEFINED
 #define GrGLSLCaps_DEFINED
@@ skipping 40 matching lines @@
     const char* fbFetchColorName() const { return fFBFetchColorName; }
 
     const char* fbFetchExtensionString() const { return fFBFetchExtensionString; }
 
     bool dropsTileOnZeroDivide() const { return fDropsTileOnZeroDivide; }
 
     bool flatInterpolationSupport() const { return fFlatInterpolationSupport; }
 
     bool noperspectiveInterpolationSupport() const { return fNoPerspectiveInterpolationSupport; }
 
+    bool multisampleInterpolationSupport() const { return fMultisampleInterpolationSupport; }
+
     bool sampleVariablesSupport() const { return fSampleVariablesSupport; }
 
     bool sampleMaskOverrideCoverageSupport() const { return fSampleMaskOverrideCoverageSupport; }
 
     AdvBlendEqInteraction advBlendEqInteraction() const { return fAdvBlendEqInteraction; }
 
     bool mustEnableAdvBlendEqs() const {
         return fAdvBlendEqInteraction >= kGeneralEnable_AdvBlendEqInteraction;
     }
 
@@ skipping 40 matching lines @@
 
     const char* externalTextureExtensionString() const {
         return fExternalTextureExtensionString;
     }
 
     const char* noperspectiveInterpolationExtensionString() const {
         SkASSERT(this->noperspectiveInterpolationSupport());
         return fNoPerspectiveInterpolationExtensionString;
     }
 
+    const char* multisampleInterpolationExtensionString() const {
+        SkASSERT(this->multisampleInterpolationSupport());
+        return fMultisampleInterpolationExtensionString;
+    }
+
     const char* sampleVariablesExtensionString() const {
         SkASSERT(this->sampleVariablesSupport());
         return fSampleVariablesExtensionString;
     }
 
     /**
      * Given a texture's config, this determines what swizzle must be appended to accesses to the
      * texture in generated shader code. Swizzling may be implemented in texture parameters or a
      * sampler rather than in the shader. In this case the returned swizzle will always be "rgba".
      */
@@ skipping 19 matching lines @@
     GrGLSLGeneration fGLSLGeneration;
     
     bool fDropsTileOnZeroDivide : 1;
     bool fFBFetchSupport : 1;
     bool fFBFetchNeedsCustomOutput : 1;
     bool fBindlessTextureSupport : 1;
     bool fUsesPrecisionModifiers : 1;
     bool fCanUseAnyFunctionInShader : 1;
     bool fFlatInterpolationSupport : 1;
     bool fNoPerspectiveInterpolationSupport : 1;
+    bool fMultisampleInterpolationSupport : 1;
     bool fSampleVariablesSupport : 1;
     bool fSampleMaskOverrideCoverageSupport : 1;
 
     // Used for specific driver bug work arounds
     bool fCanUseMinAndAbsTogether : 1;
     bool fMustForceNegatedAtanParamToFloat : 1;
 
     const char* fVersionDeclString;
 
     const char* fShaderDerivativeExtensionString;
     const char* fFragCoordConventionsExtensionString;
     const char* fSecondaryOutputExtensionString;
     const char* fExternalTextureExtensionString;
     const char* fNoPerspectiveInterpolationExtensionString;
+    const char* fMultisampleInterpolationExtensionString;
     const char* fSampleVariablesExtensionString;
 
     const char* fFBFetchColorName;
     const char* fFBFetchExtensionString;
 
     AdvBlendEqInteraction fAdvBlendEqInteraction;
 
     GrSwizzle fConfigTextureSwizzle[kGrPixelConfigCnt];
     GrSwizzle fConfigOutputSwizzle[kGrPixelConfigCnt];
 
     friend class GrGLCaps;  // For initialization.
     friend class GrVkCaps;
 
     typedef GrShaderCaps INHERITED;
 };
 
 #endif