Update XPF invariant info to not account for conflation

include/gpu/GrPaint.h

Index: include/gpu/GrPaint.h
diff --git a/include/gpu/GrPaint.h b/include/gpu/GrPaint.h
index bf2969311507495958c76e0ae4750e0c195e352a..75d3a2d0da6b1c24cf38c7f1ca17a8a98b510ddc 100644
--- a/include/gpu/GrPaint.h
+++ b/include/gpu/GrPaint.h
@@ -129,10 +129,12 @@ public:
     }
 
     /**
-     * Returns true if isOpaque would return true and the paint represents a solid constant color
-     * draw. If the result is true, constantColor will be updated to contain the constant color.
+     * Returns true if the paint's output color will be constant after blending. If the result is
+     * true, constantColor will be updated to contain the constant color. Note that we can conflate
+     * coverage and color, so the actual values written to pixels with partial coverage may still
+     * not seem constant, even if this function returns true.
      */
-    bool isOpaqueAndConstantColor(GrColor* constantColor) const;
+    bool isConstantBlendedColor(GrColor* constantColor) const;
 
 private:
     mutable SkAutoTUnref<const GrXPFactory> fXPFactory;