Bug 1002527 - Fix not to initialize remote browser's ContentParent twice. r=bent

ContentParent::GetNewOrUsed() initialize the ContentParent always, even it is an
initialized one from PreallocatedProcessManager::Take(). Initialize twice makes
ContentParent to receive two the same observed event, and creates leak in both
observer list and itself.

dom/ipc/ContentParent.cpp

@@ -598,9 +598,9 @@ ContentParent::GetNewOrUsed(bool aForBrowserElement)
                               aForBrowserElement,
                               /* isForPreallocated = */ false,
                               PROCESS_PRIORITY_FOREGROUND);
+        p->Init();
     }
 
-    p->Init();
     sNonAppContentParents->AppendElement(p);
     return p.forget();
 }