Revert of Add infastructure for gl_SampleMask

src/gpu/glsl/GrGLSLShaderBuilder.h

Index: src/gpu/glsl/GrGLSLShaderBuilder.h
diff --git a/src/gpu/glsl/GrGLSLShaderBuilder.h b/src/gpu/glsl/GrGLSLShaderBuilder.h
index cc34e44f77221bf6219b4cfa345f0bbfd5f35fe0..fa1b8e6c2f4f2ad7d5585a838fb815e15e9b6759 100644
--- a/src/gpu/glsl/GrGLSLShaderBuilder.h
+++ b/src/gpu/glsl/GrGLSLShaderBuilder.h
@@ -131,17 +131,14 @@
         kBlendFuncExtended_GLSLPrivateFeature,
         kExternalTexture_GLSLPrivateFeature,
         kFramebufferFetch_GLSLPrivateFeature,
-        kSampleMaskOverrideCoverage_GLSLPrivateFeature,
         kNoPerspectiveInterpolation_GLSLPrivateFeature,
         kLastGLSLPrivateFeature = kNoPerspectiveInterpolation_GLSLPrivateFeature
     };
 
     /*
      * A general function which enables an extension in a shader if the feature bit is not present
-     *
-     * @return true if the feature bit was not yet present, false otherwise.
-     */
-    bool addFeature(uint32_t featureBit, const char* extensionName);
+     */
+    void addFeature(uint32_t featureBit, const char* extensionName);
 
     enum InterfaceQualifier {
         kOut_InterfaceQualifier,