diff --git a/image/public/imgIContainer.idl b/image/public/imgIContainer.idl
index 2b50e4b6b6e..8cdac3facd4 100644
--- a/image/public/imgIContainer.idl
+++ b/image/public/imgIContainer.idl
@@ -57,7 +57,7 @@ native nsSize(nsSize);
  *
  * Internally, imgIContainer also manages animation of images.
  */
-[scriptable, builtinclass, uuid(4c04b27c-7a4b-4676-b04f-402ace3c3dca)]
+[scriptable, builtinclass, uuid(b56906e9-830c-45f4-b572-8c71e7619dad)]
 interface imgIContainer : nsISupports
 {
   /**
@@ -303,4 +303,17 @@ interface imgIContainer : nsISupports
    * animated), returns -1.
    */
   [notxpcom] int32_t getFirstFrameDelay();
+
+  /*
+   * If this is an animated image that hasn't started animating already, this
+   * sets the animation's start time to the indicated time.
+   *
+   * This has no effect if the image isn't animated or it has started animating
+   * already; it also has no effect if the image format doesn't care about
+   * animation start time.
+   *
+   * In all cases, animation does not actually begin until startAnimation(),
+   * resetAnimation(), or requestRefresh() is called for the first time.
+   */
+  [notxpcom] void setAnimationStartTime([const] in TimeStamp aTime);
 };
diff --git a/image/src/ImageWrapper.cpp b/image/src/ImageWrapper.cpp
index 58abe90785a..cd929145a1e 100644
--- a/image/src/ImageWrapper.cpp
+++ b/image/src/ImageWrapper.cpp
@@ -285,5 +285,11 @@ ImageWrapper::GetFirstFrameDelay()
   return mInnerImage->GetFirstFrameDelay();
 }
 
+NS_IMETHODIMP_(void)
+ImageWrapper::SetAnimationStartTime(const mozilla::TimeStamp& aTime)
+{
+  mInnerImage->SetAnimationStartTime(aTime);
+}
+
 } // namespace image
 } // namespace mozilla
diff --git a/image/src/RasterImage.cpp b/image/src/RasterImage.cpp
index 5151ee1cd78..6217f99ae19 100644
--- a/image/src/RasterImage.cpp
+++ b/image/src/RasterImage.cpp
@@ -1560,7 +1560,9 @@ RasterImage::StartAnimation()
 
     // We need to set the time that this initial frame was first displayed, as
     // this is used in AdvanceFrame().
-    mAnim->currentAnimationFrameTime = TimeStamp::Now();
+    if (mAnim->currentAnimationFrameTime.IsNull()) {
+      mAnim->currentAnimationFrameTime = TimeStamp::Now();
+    }
   }
 
   return NS_OK;
@@ -1619,6 +1621,17 @@ RasterImage::ResetAnimation()
   return NS_OK;
 }
 
+//******************************************************************************
+// [notxpcom] void requestRefresh ([const] in TimeStamp aTime);
+NS_IMETHODIMP_(void)
+RasterImage::SetAnimationStartTime(const mozilla::TimeStamp& aTime)
+{
+  if (mError || mAnimating || !mAnim)
+    return;
+
+  mAnim->currentAnimationFrameTime = aTime;
+}
+
 NS_IMETHODIMP_(float)
 RasterImage::GetFrameIndex(uint32_t aWhichFrame)
 {
diff --git a/image/src/VectorImage.cpp b/image/src/VectorImage.cpp
index e1850511d54..04305d8b061 100644
--- a/image/src/VectorImage.cpp
+++ b/image/src/VectorImage.cpp
@@ -438,6 +438,12 @@ VectorImage::ShouldAnimate()
   return ImageResource::ShouldAnimate() && mIsFullyLoaded && mHaveAnimations;
 }
 
+NS_IMETHODIMP_(void)
+VectorImage::SetAnimationStartTime(const mozilla::TimeStamp& aTime)
+{
+  // We don't care about animation start time.
+}
+
 //------------------------------------------------------------------------------
 // imgIContainer methods