Bug 1045752 - Change ScopedXErrorHandler assert to warn; r=karlt

gfx/src/X11Util.cpp

@@ -59,7 +59,9 @@ ScopedXErrorHandler::ErrorHandler(Display *, XErrorEvent *ev)
 
 ScopedXErrorHandler::ScopedXErrorHandler()
 {
-    MOZ_ASSERT(NS_IsMainThread());
+    // Off main thread usage is not safe in general, but OMTC GL layers uses this
+    // with the main thread blocked, which makes it safe.
+    NS_WARN_IF_FALSE(NS_IsMainThread(), "ScopedXErrorHandler being called off main thread, may cause issues");
     // let sXErrorPtr point to this object's mXError object, but don't reset this mXError object!
     // think of the case of nested ScopedXErrorHandler's.
     mOldXErrorPtr = sXErrorPtr;