Be a little smarter about handling the mess that is broken images. Only look

for a frame if we've had a frame at some point in the past; this should keep us
from calling GetPrimaryFrameFor quite so much during pageload.  Bug 225848,
r+sr=jst

content/base/src/nsImageLoadingContent.cpp

@@ -74,7 +74,8 @@ nsIIOService* nsImageLoadingContent::sIOService = nsnull;
 nsImageLoadingContent::nsImageLoadingContent()
   : mObserverList(nsnull),
     mLoadingEnabled(PR_TRUE),
-    mImageIsBlocked(PR_FALSE)
+    mImageIsBlocked(PR_FALSE),
+    mHaveHadObserver(PR_FALSE)
 {
   if (!sImgLoader)
     mLoadingEnabled = PR_FALSE;
@@ -243,6 +244,8 @@ nsImageLoadingContent::AddObserver(imgIDecoderObserver* aObserver)
 {
   NS_ENSURE_ARG_POINTER(aObserver);
 
+  mHaveHadObserver = PR_TRUE;
+  
   if (!mObserverList.mObserver) {
     mObserverList.mObserver = aObserver;
     // Don't touch the linking of the list!
@@ -429,8 +432,10 @@ nsImageLoadingContent::ImageURIChanged(const nsACString& aNewURI)
   // It may be that one of our frames has replaced itself with alt text... This
   // would only have happened if our mCurrentRequest had issues, and we would
   // have set it to null by now in that case.  Have to save that information
-  // here, since LoadImage may clobber the value of mCurrentRequest.
-  PRBool mayNeedReframe = !mCurrentRequest;
+  // here, since LoadImage may clobber the value of mCurrentRequest.  On the
+  // other hand, if we've never had an observer, we know there aren't any frames
+  // that have changed to alt text on us yet.
+  PRBool mayNeedReframe = mHaveHadObserver && !mCurrentRequest;
   
   // XXXbz using "documentURI" for the initialDocumentURI is not quite
   // right, but the best we can do here...

content/base/src/nsImageLoadingContent.h

@@ -177,6 +177,7 @@ private:
 
   PRPackedBool mLoadingEnabled;
   PRPackedBool mImageIsBlocked;
+  PRPackedBool mHaveHadObserver;
 };
 
 #endif // nsImageLoadingContent_h__

layout/generic/nsImageFrame.cpp

@@ -307,6 +307,9 @@ nsImageFrame::Init(nsIPresContext*  aPresContext,
 
   nsCOMPtr<nsIImageLoadingContent> imageLoader = do_QueryInterface(aContent);
   NS_ENSURE_TRUE(imageLoader, NS_ERROR_UNEXPECTED);
+  // XXXbz this call _has_ to happen before we decide we won't be rendering the
+  // image, just in case -- this lets the image loading content know someone
+  // cares.
   imageLoader->AddObserver(mListener);
 
   LoadIcons(aPresContext);

layout/html/base/src/nsImageFrame.cpp

@@ -307,6 +307,9 @@ nsImageFrame::Init(nsIPresContext*  aPresContext,
 
   nsCOMPtr<nsIImageLoadingContent> imageLoader = do_QueryInterface(aContent);
   NS_ENSURE_TRUE(imageLoader, NS_ERROR_UNEXPECTED);
+  // XXXbz this call _has_ to happen before we decide we won't be rendering the
+  // image, just in case -- this lets the image loading content know someone
+  // cares.
   imageLoader->AddObserver(mListener);
 
   LoadIcons(aPresContext);