Backed out changeset 24ec7aba60e7 (bug 1283302) for testfailures in 518172-1b.html

layout/base/nsPresShell.h

@@ -66,9 +66,9 @@ typedef nsClassHashtable<nsUint64HashKey, mozilla::CSSIntRegion> VisibleRegions;
 
 } // namespace mozilla
 
-// 5ms.  This is actually pref-controlled, but we use this value if we fail
+// 250ms.  This is actually pref-controlled, but we use this value if we fail
 // to get the pref for any reason.
-#define PAINTLOCK_EVENT_DELAY 5
+#define PAINTLOCK_EVENT_DELAY 250
 
 class PresShell final : public nsIPresShell,
                         public nsStubDocumentObserver,