Switch to a Promise-based version of DevTools interaction

src/application-delegate.coffee

@@ -66,10 +66,26 @@ class ApplicationDelegate
     ipc.send("call-window-method", "setFullScreen", fullScreen)
 
   openWindowDevTools: ->
-    ipc.send("call-window-method", "openDevTools")
+    if remote.getCurrentWindow().isDevToolsOpened()
+      Promise.resolve()
+    else
+      new Promise (resolve) ->
+        remote.getCurrentWindow().once("devtools-opened", -> resolve())
+        ipc.send("call-window-method", "openDevTools")
+
+  closeWindowDevTools: ->
+    unless remote.getCurrentWindow().isDevToolsOpened()
+      Promise.resolve()
+    else
+      new Promise (resolve) ->
+        remote.getCurrentWindow().once("devtools-closed", -> resolve())
+        ipc.send("call-window-method", "closeDevTools")
 
   toggleWindowDevTools: ->
-    ipc.send("call-window-method", "toggleDevTools")
+    if remote.getCurrentWindow().isDevToolsOpened()
+      @closeWindowDevTools()
+    else
+      @openWindowDevTools()
 
   executeJavaScriptInWindowDevTools: (code) ->
     ipc.send("call-window-method", "executeJavaScriptInDevTools", code)

src/atom-environment.coffee

@@ -670,8 +670,7 @@ class AtomEnvironment extends Model
       @emitter.emit 'will-throw-error', eventObject
 
       if openDevTools
-        @openDevTools()
-        @executeJavaScriptInDevTools('DevToolsAPI.showConsole()')
+        @openDevTools().then => @executeJavaScriptInDevTools('DevToolsAPI.showConsole()')
 
       @emitter.emit 'did-throw-error', {message, url, line, column, originalError}
 
@@ -721,10 +720,15 @@ class AtomEnvironment extends Model
   ###
 
   # Extended: Open the dev tools for the current window.
+  #
+  # Returns a {Promise} that resolves when the DevTools have been opened.
   openDevTools: ->
     @applicationDelegate.openWindowDevTools()
 
   # Extended: Toggle the visibility of the dev tools for the current window.
+  #
+  # Returns a {Promise} that resolves when the DevTools have been opened or
+  # closed.
   toggleDevTools: ->
     @applicationDelegate.toggleWindowDevTools()