added support for glMinSampleShading

src/gpu/GrGeometryProcessor.h

Index: src/gpu/GrGeometryProcessor.h
diff --git a/src/gpu/GrGeometryProcessor.h b/src/gpu/GrGeometryProcessor.h
index 05afd5329a20dd9694b44dea6d83db3009f07c5e..1dbf1539a22bbb86d31bd45ad964d47ab87b15fa 100644
--- a/src/gpu/GrGeometryProcessor.h
+++ b/src/gpu/GrGeometryProcessor.h
@@ -21,7 +21,8 @@ class GrGeometryProcessor : public GrPrimitiveProcessor {
 public:
     GrGeometryProcessor()
         : fWillUseGeoShader(false)
-        , fLocalCoordsType(kUnused_LocalCoordsType) {}
+        , fLocalCoordsType(kUnused_LocalCoordsType)
+        , fSampleShading(0.0) {}
 
     bool willUseGeoShader() const override { return fWillUseGeoShader; }
 
@@ -33,6 +34,15 @@ public:
         return kHasExplicit_LocalCoordsType == fLocalCoordsType;
     }
 
+    /**
+     * Returns the minimum fraction of samples for which the fragment shader will be run. For
+     * instance, if sampleShading is 0.5 in MSAA16 mode, the fragment shader will run a minimum of
+     * 8 times per pixel. The default value is zero.
+     */
+    float getSampleShading() const override {
+        return fSampleShading;
+    }
+
 protected:
     /**
      * Subclasses call this from their constructor to register vertex attributes.  Attributes
@@ -74,9 +84,14 @@ protected:
         fLocalCoordsType = kHasTransformed_LocalCoordsType;
     }
 
+    void setSampleShading(float sampleShading) {
+        fSampleShading = sampleShading;
+    }
+
 private:
     bool fWillUseGeoShader;
     LocalCoordsType fLocalCoordsType;
+    float fSampleShading;
 
     typedef GrPrimitiveProcessor INHERITED;
 };