Implements getImageAnimationPolicy() at ImageLoader.

Source/platform/graphics/BitmapImage.cpp

Index: Source/platform/graphics/BitmapImage.cpp
diff --git a/Source/platform/graphics/BitmapImage.cpp b/Source/platform/graphics/BitmapImage.cpp
index a937da22617ae000cc3bec3b2157c5e1582a433e..8ffafb8cb36399ff81cda5afcf3153a0b66f22b8 100644
--- a/Source/platform/graphics/BitmapImage.cpp
+++ b/Source/platform/graphics/BitmapImage.cpp
@@ -599,6 +599,14 @@ bool BitmapImage::maybeAnimated()
     return m_source.repetitionCount() != cAnimationNone;
 }
 
+void BitmapImage::advanceTime(double deltaTimeInSeconds)
+{
+    if (m_desiredFrameStartTime)
+        m_desiredFrameStartTime -= deltaTimeInSeconds;
+    else
+        m_desiredFrameStartTime = monotonicallyIncreasingTime() - deltaTimeInSeconds;
+}
+
 void BitmapImage::advanceAnimation(Timer<BitmapImage>*)
 {
     internalAdvanceAnimation(false);