[network] Fix CacheEntry::mDoomCallback data race.

netwerk/cache2/CacheEntry.cpp

@@ -481,7 +481,12 @@ NS_IMETHODIMP CacheEntry::OnFileReady(nsresult aResult, bool aIsNew)
 
 NS_IMETHODIMP CacheEntry::OnFileDoomed(nsresult aResult)
 {
-  if (mDoomCallback) {
+  bool doomCallback = false;
+  {
+    mozilla::MutexAutoLock lock(mLock);
+    doomCallback = bool(mDoomCallback);
+  }
+  if (doomCallback) {
     RefPtr<DoomCallbackRunnable> event =
       new DoomCallbackRunnable(this, aResult);
     NS_DispatchToMainThread(event);
@@ -1738,8 +1743,13 @@ void CacheEntry::DoomFile()
     }
   }
 
-  // Always posts to the main thread.
+  // mLock is already held in the caller; dispatch directly
-  OnFileDoomed(rv);
+  // instead of calling OnFileDoomed() which would deadlock when
+  // re-acquiring the lock.
+  if (mDoomCallback) {
+    RefPtr<DoomCallbackRunnable> event = new DoomCallbackRunnable(this, rv);
+    NS_DispatchToMainThread(event);
+  }
 }
 
 void CacheEntry::RemoveForcedValidity()