Bug 1155059: Patch 6 - fix problems with gfxFontInfoLoader shutdown sequence r=jdaggett

gfx/thebes/gfxFontInfoLoader.cpp

@@ -66,7 +66,6 @@ FontInfoLoadCompleteEvent::Run()
 
     loader->FinalizeLoader(mFontInfo);
 
-    mFontInfo = nullptr;
     return NS_OK;
 }
 
@@ -81,7 +80,6 @@ AsyncFontInfoLoader::Run()
 
     // post a completion event that transfer the data to the fontlist
     NS_DispatchToMainThread(mCompleteEvent);
-    mFontInfo = nullptr;
 
     return NS_OK;
 }
@@ -140,23 +138,27 @@ gfxFontInfoLoader::StartLoader(uint32_t aDelay, uint32_t aInterval)
     InitLoader();
 
     // start async load
-    mState = stateAsyncLoad;
     nsresult rv = NS_NewNamedThread("Font Loader",
                                     getter_AddRefs(mFontLoaderThread),
                                     nullptr);
-    if (NS_FAILED(rv)) {
+    if (NS_WARN_IF(NS_FAILED(rv))) {
         return;
     }
+    mState = stateAsyncLoad;
 
     nsCOMPtr<nsIRunnable> loadEvent = new AsyncFontInfoLoader(mFontInfo);
 
-    mFontLoaderThread->Dispatch(loadEvent, NS_DISPATCH_NORMAL);
+    mFontLoaderThread->Dispatch(loadEvent.forget(), NS_DISPATCH_NORMAL);
 }
 
 void
 gfxFontInfoLoader::FinalizeLoader(FontInfoData *aFontInfo)
 {
-    // avoid loading data if loader has already been canceled
+    // Avoid loading data if loader has already been canceled.
+    // This should mean that CancelLoader() ran and the Load
+    // thread has already Shutdown(), and likely before processing
+    // the Shutdown event it handled the load event and sent back
+    // our Completion event, thus we end up here.
     if (mState != stateAsyncLoad) {
         return;
     }
@@ -187,8 +189,11 @@ gfxFontInfoLoader::CancelLoader()
         mTimer = nullptr;
     }
     if (mFontLoaderThread) {
-        mFontLoaderThread->Shutdown();
-        mFontLoaderThread = nullptr;
+        // NOTE: Shutdown() runs the event loop, and we can get timer events
+        // ensure that we can't try to do this twice!
+        nsCOMPtr<nsIThread> temp;
+        temp.swap(mFontLoaderThread);
+        temp->Shutdown();
     }
     RemoveShutdownObserver();
     CleanupLoader();