Bug 860879 - Make file picker use public PromptService.getResponse method; r=wesj
Bug 860879 - Refactor PromptService; r=wesj
Bug 860879 - Make GeckoAppShell.processNextNativeEvent waitable; r=blassey
Bug 860879 - Make PromptService not block when handing result from UI to Gecko thread; r=wesj
Bug 860879 - Make file picker not block when handing result from UI to Gecko thread; r=wesj