Bug 1142841: Convert all nsRefPtr<nsIRunnable> to nsCOMPtr<nsIRunnable>. r=ehsan

This patch was generated by a script.  Here's the source of the script for
future reference:

find . \( -iname "*.cpp" -o -iname "*.h" \) | \
  xargs -n 1 sed -i "s/nsRefPtr<nsIRunnable>/nsCOMPtr<nsIRunnable>/g"

xpcom/base/AvailableMemoryTracker.cpp

@@ -469,7 +469,7 @@ nsMemoryPressureWatcher::Observe(nsISupports* aSubject, const char* aTopic,
   MOZ_ASSERT(!strcmp(aTopic, "memory-pressure"), "Unknown topic");
 
   if (sFreeDirtyPages) {
-    nsRefPtr<nsIRunnable> runnable = new nsJemallocFreeDirtyPagesRunnable();
+    nsCOMPtr<nsIRunnable> runnable = new nsJemallocFreeDirtyPagesRunnable();
 
     NS_DispatchToMainThread(runnable);
   }