--- a/browser/devtools/framework/test/browser.ini
+++ b/browser/devtools/framework/test/browser.ini
@@ -14,16 +14,17 @@ skip-if = e10s # Bug 1070837 - devtools/
 [browser_dynamic_tool_enabling.js]
 [browser_keybindings.js]
 [browser_new_activation_workflow.js]
 [browser_target_events.js]
 [browser_target_remote.js]
 [browser_target_support.js]
 [browser_two_tabs.js]
 [browser_toolbox_dynamic_registration.js]
+[browser_toolbox_getpanelwhenready.js]
 [browser_toolbox_highlight.js]
 [browser_toolbox_hosts.js]
 [browser_toolbox_options.js]
 [browser_toolbox_options_devedition.js]
 [browser_toolbox_options_disable_buttons.js]
 [browser_toolbox_options_disable_cache.js]
 skip-if = e10s # Bug 1030318
 [browser_toolbox_options_disable_js.js]

new file mode 100644
--- /dev/null
+++ b/browser/devtools/framework/test/browser_toolbox_getpanelwhenready.js
@@ -0,0 +1,34 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Tests that getPanelWhenReady returns the correct panel in promise
+// resolutions regardless of whether it has opened first.
+
+let toolbox = null;
+
+const URL = "data:text/html;charset=utf8,test for getPanelWhenReady";
+
+let test = asyncTest(function*() {
+  let tab = yield addTab(URL);
+  let target = TargetFactory.forTab(tab);
+  toolbox = yield gDevTools.showToolbox(target);
+
+  let debuggerPanelPromise = toolbox.getPanelWhenReady("jsdebugger");
+  yield toolbox.selectTool("jsdebugger");
+  let debuggerPanel = yield debuggerPanelPromise;
+
+  is (debuggerPanel, toolbox.getPanel("jsdebugger"),
+      "The debugger panel from getPanelWhenReady before loading is the actual panel");
+
+  let debuggerPanel2 = yield toolbox.getPanelWhenReady("jsdebugger");
+  is (debuggerPanel2, toolbox.getPanel("jsdebugger"),
+      "The debugger panel from getPanelWhenReady after loading is the actual panel");
+
+  yield cleanup();
+});
+
+function* cleanup() {
+  yield toolbox.destroy();
+  gBrowser.removeCurrentTab();
+  toolbox = null;
+}

--- a/browser/devtools/framework/toolbox.js
+++ b/browser/devtools/framework/toolbox.js
@@ -170,16 +170,43 @@ Toolbox.prototype = {
   /**
    * Access the panel for a given tool
    */
   getPanel: function(id) {
     return this._toolPanels.get(id);
   },
 
   /**
+   * Get the panel instance for a given tool once it is ready.
+   * If the tool is already opened, the promise will resolve immediately,
+   * otherwise it will wait until the tool has been opened before resolving.
+   *
+   * Note that this does not open the tool, use selectTool if you'd
+   * like to select the tool right away.
+   *
+   * @param  {String} id
+   *         The id of the panel, for example "jsdebugger".
+   * @returns Promise
+   *          A promise that resolves once the panel is ready.
+   */
+  getPanelWhenReady: function(id) {
+    let deferred = promise.defer();
+    let panel = this.getPanel(id);
+    if (panel) {
+      deferred.resolve(panel);
+    } else {
+      this.on(id + "-ready", (e, panel) => {
+        deferred.resolve(panel);
+      });
+    }
+
+    return deferred.promise;
+  },
+
+  /**
    * This is a shortcut for getPanel(currentToolId) because it is much more
    * likely that we're going to want to get the panel that we've just made
    * visible
    */
   getCurrentPanel: function() {
     return this._toolPanels.get(this.currentToolId);
   },