Reset animation state when animation policy is changed.

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 e80ebe3106ad8ba91036a34e0dc1a81278c77e95..2f55a9990214832b73ca1711078be29a90be978f 100644
--- a/Source/platform/graphics/BitmapImage.cpp
+++ b/Source/platform/graphics/BitmapImage.cpp
@@ -443,7 +443,10 @@ bool BitmapImage::shouldAnimate()
 {
     bool animated = repetitionCount(false) != cAnimationNone && !m_animationFinished && imageObserver();
     if (imageObserver()) {
+        ImageAnimationPolicy oldPolicy = m_animationPolicy;
         imageObserver()->imageAnimationPolicy(this, m_animationPolicy);
+        if (oldPolicy != m_animationPolicy)
+            resetAnimation();
         if (animated && m_animationPolicy == ImageAnimationPolicyNoAnimation)
             animated = false;
     }