DM: find max component difference

dm/DMUtil.h

Index: dm/DMUtil.h
diff --git a/dm/DMUtil.h b/dm/DMUtil.h
index 535d9f26db055667d23b503448b5947c47071404..b5b5e3203bf9b0388dc7a07efd58a37bbbf0303c 100644
--- a/dm/DMUtil.h
+++ b/dm/DMUtil.h
@@ -28,6 +28,9 @@ void AllocatePixels(const SkBitmap& reference, SkBitmap* bitmap);
 // Draw picture to bitmap.
 void DrawPicture(SkPicture* picture, SkBitmap* bitmap);
 
+// What is the maximum component difference in these bitmaps?
+unsigned MaxComponentDifference(const SkBitmap& a, const SkBitmap& b);

[reed1, 2014/05/16 12:30:00]

For the future, it might prove useful to return 4 values, one for each
component, as that may be interesting to the operator. Not for this CL per-se.

[mtklein, 2014/05/16 13:00:53]

Agreed.

+
 // Are these identical bitmaps?
 bool BitmapsEqual(const SkBitmap& a, const SkBitmap& b);