Add scale param to SkAlphaThresholdFilter.

include/effects/SkAlphaThresholdFilter.h

Index: include/effects/SkAlphaThresholdFilter.h
diff --git a/include/effects/SkAlphaThresholdFilter.h b/include/effects/SkAlphaThresholdFilter.h
index 23af56fc549aea172698b58096ebb4a35f3cb590..860829508bac25f990fcb767b7de521012060acc 100644
--- a/include/effects/SkAlphaThresholdFilter.h
+++ b/include/effects/SkAlphaThresholdFilter.h
@@ -21,6 +21,19 @@ public:
      * source image.
      */
     static SkImageFilter* Create(const SkRegion& region, SkScalar innerThreshold, SkScalar outerThreshold);
+
+    /**
+     * Creates an image filter that samples a region. If the sample is inside the
+     * region the alpha of the image is boosted up to a threshold value. If it is
+     * outside the region then the alpha is decreased to the threshold value.
+     * The 0,0 point of the region corresponds to the upper left corner of the
+     * source image.
+     * Since the image pixels are in device units but the |region| is in device-
+     * independent units, the |transform| is applied to the |region| so that it
+     * matches the pixels.
+     */
+    static SkImageFilter* Create(const SkRegion& region, const SkMatrix& transform,
+                                 SkScalar innerThreshold, SkScalar outerThreshold);
 };
 
 #endif