diff --git a/image/public/imgIContainer.idl b/image/public/imgIContainer.idl
index 5a632215103f..14d22f2c554b 100644
--- a/image/public/imgIContainer.idl
+++ b/image/public/imgIContainer.idl
@@ -93,7 +93,7 @@ native gfxGraphicsFilter(gfxPattern::GraphicsFilter);
  *
  * Internally, imgIContainer also manages animation of images.
  */
-[scriptable, uuid(2506249c-e0a1-4d8f-846c-2d478247f8d8)]
+[scriptable, uuid(8bf87433-be67-413b-9497-00071c5002bd)]
 interface imgIContainer : nsISupports
 {
   /**
@@ -283,6 +283,12 @@ interface imgIContainer : nsISupports
     */
   void unlockImage();
 
+  /**
+   * If this image is unlocked, discard its decoded data.  If the image is
+   * locked or has already been discarded, do nothing.
+   */
+  void requestDiscard();
+
   /**
     * Indicates that this imgIContainer has been triggered to update
     * its internal animation state. Likely this should only be called
diff --git a/image/public/imgIRequest.idl b/image/public/imgIRequest.idl
index 9d3cfb75b925..080e2f9661ba 100644
--- a/image/public/imgIRequest.idl
+++ b/image/public/imgIRequest.idl
@@ -52,7 +52,7 @@ interface nsIPrincipal;
  * @version 0.1
  * @see imagelib2
  */
-[scriptable, uuid(c3bf4e2a-f64b-4ac1-a84e-18631b1802ab)]
+[scriptable, uuid(d35a9adb-8328-4b64-b06f-72a165acd080)]
 interface imgIRequest : nsIRequest
 {
   /**
@@ -194,6 +194,12 @@ interface imgIRequest : nsIRequest
    */
   void unlockImage();
 
+  /**
+   * If this image is unlocked, discard the image's decoded data.  If the image
+   * is locked or is already discarded, do nothing.
+   */
+  void requestDiscard();
+
   /**
    * If this request is for an animated image, the method creates a new
    * request which contains the current frame of the image.
diff --git a/image/src/RasterImage.cpp b/image/src/RasterImage.cpp
index c591d117a19e..d7df5408b477 100644
--- a/image/src/RasterImage.cpp
+++ b/image/src/RasterImage.cpp
@@ -2181,8 +2181,7 @@ RasterImage::Discard(bool force)
   if (observer)
     observer->OnDiscard(nsnull);
 
-  if (force)
-    DiscardTracker::Remove(&mDiscardTrackerNode);
+  DiscardTracker::Remove(&mDiscardTrackerNode);
 
   // Log
   PR_LOG(gCompressedImageAccountingLog, PR_LOG_DEBUG,
@@ -2695,6 +2694,18 @@ RasterImage::UnlockImage()
   return NS_OK;
 }
 
+//******************************************************************************
+/* void requestDiscard() */
+NS_IMETHODIMP
+RasterImage::RequestDiscard()
+{
+  if (CanDiscard()) {
+    Discard();
+  }
+
+  return NS_OK;
+}
+
 // Flushes up to aMaxBytes to the decoder.
 nsresult
 RasterImage::DecodeSomeData(PRUint32 aMaxBytes)
diff --git a/image/src/RasterImage.h b/image/src/RasterImage.h
index 95baaa8bef0a..a3f9a5c41b2f 100644
--- a/image/src/RasterImage.h
+++ b/image/src/RasterImage.h
@@ -198,6 +198,7 @@ public:
   NS_SCRIPTABLE NS_IMETHOD RequestDecode(void);
   NS_SCRIPTABLE NS_IMETHOD LockImage(void);
   NS_SCRIPTABLE NS_IMETHOD UnlockImage(void);
+  NS_SCRIPTABLE NS_IMETHOD RequestDiscard(void);
   NS_SCRIPTABLE NS_IMETHOD ResetAnimation(void);
   NS_IMETHOD_(void) RequestRefresh(const mozilla::TimeStamp& aTime);
   // END NS_DECL_IMGICONTAINER
diff --git a/image/src/VectorImage.cpp b/image/src/VectorImage.cpp
index f263f29d5034..530602d1b085 100644
--- a/image/src/VectorImage.cpp
+++ b/image/src/VectorImage.cpp
@@ -626,6 +626,15 @@ VectorImage::UnlockImage()
   return NS_OK;
 }
 
+//******************************************************************************
+/* void requestDiscard() */
+NS_IMETHODIMP
+VectorImage::RequestDiscard()
+{
+  // This method is for image-discarding, which only applies to RasterImages.
+  return NS_OK;
+}
+
 //******************************************************************************
 /* void resetAnimation (); */
 NS_IMETHODIMP
diff --git a/image/src/VectorImage.h b/image/src/VectorImage.h
index bd1e9b4ad497..a10a347eacc7 100644
--- a/image/src/VectorImage.h
+++ b/image/src/VectorImage.h
@@ -81,6 +81,7 @@ public:
   NS_SCRIPTABLE NS_IMETHOD RequestDecode(void);
   NS_SCRIPTABLE NS_IMETHOD LockImage(void);
   NS_SCRIPTABLE NS_IMETHOD UnlockImage(void);
+  NS_SCRIPTABLE NS_IMETHOD RequestDiscard(void);
   NS_SCRIPTABLE NS_IMETHOD ResetAnimation(void);
   NS_IMETHOD_(void) RequestRefresh(const mozilla::TimeStamp& aTime);
   // END NS_DECL_IMGICONTAINER
diff --git a/image/src/imgRequestProxy.cpp b/image/src/imgRequestProxy.cpp
index 477ee29343a6..32edcc9360a4 100644
--- a/image/src/imgRequestProxy.cpp
+++ b/image/src/imgRequestProxy.cpp
@@ -370,6 +370,16 @@ imgRequestProxy::UnlockImage()
   return NS_OK;
 }
 
+/* void requestDiscard (); */
+NS_IMETHODIMP
+imgRequestProxy::RequestDiscard()
+{
+  if (mImage) {
+    return mImage->RequestDiscard();
+  }
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 imgRequestProxy::IncrementAnimationConsumers()
 {