Bug 745662 - Trigger a fatal release-time crash when the discard tracker is used off the main thread. r=joe

image/src/DiscardTracker.cpp

@@ -45,6 +45,8 @@ DiscardTimeoutChangedCallback(const char* aPref, void *aClosure)
 nsresult
 DiscardTracker::Reset(Node *node)
 {
+  EnsureMainThread();
+
   // We shouldn't call Reset() with a null |img| pointer, on images which can't
   // be discarded, or on animated images (which should be marked as
   // non-discardable, anyway).
@@ -84,6 +86,8 @@ DiscardTracker::Reset(Node *node)
 void
 DiscardTracker::Remove(Node *node)
 {
+  EnsureMainThread();
+
   if (node->isInList())
     node->remove();
 
@@ -97,6 +101,8 @@ DiscardTracker::Remove(Node *node)
 void
 DiscardTracker::Shutdown()
 {
+  EnsureMainThread();
+
   if (sTimer) {
     sTimer->Cancel();
     sTimer = NULL;
@@ -109,6 +115,8 @@ DiscardTracker::Shutdown()
 void
 DiscardTracker::DiscardAll()
 {
+  EnsureMainThread();
+
   if (!sInitialized)
     return;
 
@@ -126,6 +134,8 @@ DiscardTracker::DiscardAll()
 void
 DiscardTracker::InformAllocation(PRInt64 bytes)
 {
+  EnsureMainThread();
+
   // This function is called back e.g. from RasterImage::Discard(); be careful!
 
   sCurrentDecodedImageBytes += bytes;
@@ -136,6 +146,17 @@ DiscardTracker::InformAllocation(PRInt64 bytes)
   MaybeDiscardSoon();
 }
 
+void
+DiscardTracker::EnsureMainThread()
+{
+  // NS_RUNTIMEABORT is a fatal crash even in release builds.  We need to crash
+  // release builds here in order to investigate bug 745141 -- we're being
+  // called from off main thread, but we don't know how!
+  if (!NS_IsMainThread()) {
+    NS_RUNTIMEABORT("Must be on main thread!");
+  }
+}
+
 /**
  * Initialize the tracker.
  */

image/src/DiscardTracker.h

@@ -100,6 +100,8 @@ class DiscardTracker
     static void TimerCallback(nsITimer *aTimer, void *aClosure);
     static void DiscardNow();
 
+    static void EnsureMainThread();
+
     static LinkedList<Node> sDiscardableImages;
     static nsCOMPtr<nsITimer> sTimer;
     static bool sInitialized;