Add special case circle blur for Ganesh

This makes the blurcircles bench go from ~33us to ~8us on Windows desktop.

It will require layout test suppressions

Review URL: https://codereview.chromium.org/1311583005
diff --git a/src/effects/SkBlurMask.h b/src/effects/SkBlurMask.h
index 5c2a82e..b6c37fb 100644
--- a/src/effects/SkBlurMask.h
+++ b/src/effects/SkBlurMask.h
@@ -54,15 +54,14 @@
         @param blurred_width The width of the final, blurred rectangle
         @param sharp_width The width of the original, unblurred rectangle.
     */
-    static uint8_t ProfileLookup(const uint8_t* profile, int loc, int blurred_width, int sharp_width);
+    static uint8_t ProfileLookup(const uint8_t* profile, int loc, int blurredWidth, int sharpWidth);
 
     /** Allocate memory for and populate the profile of a 1D blurred halfplane.  The caller
         must free the memory.  The amount of memory allocated will be exactly 6*sigma bytes.
         @param sigma The standard deviation of the gaussian blur kernel
-        @param profile_out The location to store the allocated profile curve
     */
 
-    static void ComputeBlurProfile(SkScalar sigma, uint8_t** profile_out);
+    static uint8_t* ComputeBlurProfile(SkScalar sigma);
 
     /** Compute an entire scanline of a blurred step function.  This is a 1D helper that
         will produce both the horizontal and vertical profiles of the blurry rectangle.