Animated PNG implementation

Source/platform/image-decoders/ImageFrame.h

Index: Source/platform/image-decoders/ImageFrame.h
diff --git a/Source/platform/image-decoders/ImageFrame.h b/Source/platform/image-decoders/ImageFrame.h
index fb7425755bd77887066531b171c6c8dc21c5b2d8..0a2a13162e201066bf2bb22cd146e425b8f8a5ea 100644
--- a/Source/platform/image-decoders/ImageFrame.h
+++ b/Source/platform/image-decoders/ImageFrame.h
@@ -178,6 +178,45 @@ public:
         *dest = SkPackARGB32NoCheck(a, r, g, b);
     }
 
+    inline void overRGBAPremultiply(PixelData* dest, unsigned r, unsigned g, unsigned b, unsigned a)
+    {
+        enum FractionControl { RoundFractionControl = 257 * 128 };
+
+        if (!a)
+            return;
+
+        if (a < 255) {
+            unsigned alpha = a * 257;
+            r = (r * alpha + RoundFractionControl) >> 16;
+            g = (g * alpha + RoundFractionControl) >> 16;
+            b = (b * alpha + RoundFractionControl) >> 16;
+            *dest = SkPMSrcOver(SkPackARGB32NoCheck(a, r, g, b), *dest);
+        } else {
+            *dest = SkPackARGB32NoCheck(a, r, g, b);
+        }
+    }
+
+    inline void overRGBARaw(PixelData* dest, unsigned r, unsigned g, unsigned b, unsigned a)
+    {
+        if (!a)
+            return;
+
+        unsigned aDest = SkGetPackedA32(*dest);
+        if (aDest && a < 255) {
+            unsigned u = a * 255;
+            unsigned v = (255 - a) * aDest;
+            unsigned alpha = u + v;
+            unsigned rDest = SkGetPackedR32(*dest);
+            unsigned gDest = SkGetPackedG32(*dest);
+            unsigned bDest = SkGetPackedB32(*dest);
+            a = (alpha + (alpha >> 8) + 1) >> 8;
+            r = (r * u + rDest * v) / alpha;
+            g = (g * u + gDest * v) / alpha;
+            b = (b * u + bDest * v) / alpha;
+        }
+        *dest = SkPackARGB32NoCheck(a, r, g, b);
+    }
+
     // Notifies the SkBitmap if any pixels changed and resets the flag.
     inline void notifyBitmapIfPixelsChanged()
     {