diff --git a/image/public/imgIContainer.idl b/image/public/imgIContainer.idl
index bf8bba76ca25..0b7401526806 100644
--- a/image/public/imgIContainer.idl
+++ b/image/public/imgIContainer.idl
@@ -55,7 +55,7 @@ native gfxGraphicsFilter(gfxPattern::GraphicsFilter);
  *
  * Internally, imgIContainer also manages animation of images.
  */
-[scriptable, builtinclass, uuid(01e12ac9-7d9f-40d9-9ec1-70b64c53ce7a)]
+[scriptable, builtinclass, uuid(c7e8eed7-2be9-40b0-be7c-b682097f5b28)]
 interface imgIContainer : nsISupports
 {
   /**
@@ -94,12 +94,6 @@ interface imgIContainer : nsISupports
    */
   readonly attribute boolean animated;
 
-  /**
-   * Whether the current frame is opaque; that is, needs the background painted
-   * behind it.
-   */
-  readonly attribute boolean currentFrameIsOpaque;
-
   /**
    * Flags for imgIContainer operations.
    *
@@ -152,6 +146,14 @@ interface imgIContainer : nsISupports
   [noscript] gfxASurface getFrame(in uint32_t aWhichFrame,
                                   in uint32_t aFlags);
 
+  /**
+   * Whether the given frame is opaque; that is, needs the background painted
+   * behind it.
+   *
+   * @param aWhichFrame Frame specifier of the FRAME_* variety.
+   */
+  [notxpcom] boolean frameIsOpaque(in uint32_t aWhichFrame);
+
   /**
    * Attempts to create an ImageContainer (and Image) containing the current
    * frame. Only valid for RASTER type images.
diff --git a/image/src/RasterImage.cpp b/image/src/RasterImage.cpp
index 5f5dc77bbb15..3fe392c01036 100644
--- a/image/src/RasterImage.cpp
+++ b/image/src/RasterImage.cpp
@@ -877,33 +877,32 @@ RasterImage::GetCurrentDrawableImgFrame()
 }
 
 //******************************************************************************
-/* readonly attribute boolean currentFrameIsOpaque; */
-NS_IMETHODIMP
-RasterImage::GetCurrentFrameIsOpaque(bool *aIsOpaque)
+/* [notxpcom] boolean frameIsOpaque(in uint32_t aWhichFrame); */
+NS_IMETHODIMP_(bool)
+RasterImage::FrameIsOpaque(uint32_t aWhichFrame)
 {
-  NS_ENSURE_ARG_POINTER(aIsOpaque);
-
-  if (mError)
-    return NS_ERROR_FAILURE;
-
-  // See if we can get an image frame
-  imgFrame *curframe = GetCurrentImgFrame();
-
-  // If we don't get a frame, the safe answer is "not opaque"
-  if (!curframe)
-    *aIsOpaque = false;
-
-  // Otherwise, we can make a more intelligent decision
-  else {
-    *aIsOpaque = !curframe->GetNeedsBackground();
-
-    // We are also transparent if the current frame's size doesn't cover our
-    // entire area.
-    nsIntRect framerect = curframe->GetRect();
-    *aIsOpaque = *aIsOpaque && framerect.IsEqualInterior(nsIntRect(0, 0, mSize.width, mSize.height));
+  if (aWhichFrame > FRAME_MAX_VALUE) {
+    NS_WARNING("aWhichFrame outside valid range!");
+    return false;
   }
 
-  return NS_OK;
+  if (mError)
+    return false;
+
+  // See if we can get an image frame.
+  imgFrame* frame = aWhichFrame == FRAME_FIRST ? GetImgFrame(0)
+                                               : GetCurrentImgFrame();
+
+  // If we don't get a frame, the safe answer is "not opaque".
+  if (!frame)
+    return false;
+
+  // Other, the frame is transparent if either:
+  //  1. It needs a background.
+  //  2. Its size doesn't cover our entire area.
+  nsIntRect framerect = frame->GetRect();
+  return !frame->GetNeedsBackground() &&
+         framerect.IsEqualInterior(nsIntRect(0, 0, mSize.width, mSize.height));
 }
 
 void
diff --git a/image/src/VectorImage.cpp b/image/src/VectorImage.cpp
index be67256cfb63..f983a6183d7a 100644
--- a/image/src/VectorImage.cpp
+++ b/image/src/VectorImage.cpp
@@ -383,13 +383,14 @@ VectorImage::GetAnimated(bool* aAnimated)
 }
 
 //******************************************************************************
-/* readonly attribute boolean currentFrameIsOpaque; */
-NS_IMETHODIMP
-VectorImage::GetCurrentFrameIsOpaque(bool* aIsOpaque)
+/* [notxpcom] boolean frameIsOpaque(in uint32_t aWhichFrame); */
+NS_IMETHODIMP_(bool)
+VectorImage::FrameIsOpaque(uint32_t aWhichFrame)
 {
-  NS_ENSURE_ARG_POINTER(aIsOpaque);
-  *aIsOpaque = false;   // In general, SVG content is not opaque.
-  return NS_OK;
+  if (aWhichFrame > FRAME_MAX_VALUE)
+    NS_WARNING("aWhichFrame outside valid range!");
+
+  return false; // In general, SVG content is not opaque.
 }
 
 //******************************************************************************
diff --git a/layout/style/nsStyleStruct.cpp b/layout/style/nsStyleStruct.cpp
index 66eca3a58369..5d57be367a84 100644
--- a/layout/style/nsStyleStruct.cpp
+++ b/layout/style/nsStyleStruct.cpp
@@ -1643,10 +1643,8 @@ nsStyleImage::IsOpaque() const
   mImage->GetImage(getter_AddRefs(imageContainer));
   NS_ABORT_IF_FALSE(imageContainer, "IsComplete() said image container is ready");
 
-  // Check if the crop region of the current image frame is opaque
-  bool isOpaque;
-  if (NS_SUCCEEDED(imageContainer->GetCurrentFrameIsOpaque(&isOpaque)) &&
-      isOpaque) {
+  // Check if the crop region of the current image frame is opaque.
+  if (imageContainer->FrameIsOpaque(imgIContainer::FRAME_CURRENT)) {
     if (!mCropRect)
       return true;