Bug 989046 - a. Convert Gecko side messaging to use NativeJSContainer; r=blassey
Bug 989046 - b. Drop JSON.stringify when calling handleGeckoMessage; r=mfinkle
Bug 989046 - c. Support multiple listener types in EventDispatcher; r=mfinkle
Bug 989046 - d. Register prompt event on startup; r=liuche
Bug 989046 - e. Only unregister event in FindInPageBar if already registered; r=capella
Bug 989046 - f. Only unregister event in GeckoEditable if already registered; r=capella
Bug 989046 - g. Only unregister event in BrowserHealthRecorder if already registered; r=rnewman
Bug 989046 - h. Be more strict about event registration in non-release versions; r=mfinkle