Bug 1448499 - Destroy deviceFront when destroying the toolbox;r=jryans

MozReview-Commit-ID: IMlKbiaUKu7

--HG--
extra : rebase_source : 746806af98af61f3db7aea732654c766c594bd03

devtools/client/framework/toolbox.js

@@ -71,6 +71,8 @@ loader.lazyRequireGetter(this, "StyleSheetsFront",
   "devtools/shared/fronts/stylesheets", true);
 loader.lazyRequireGetter(this, "buildHarLog",
   "devtools/client/netmonitor/src/har/har-builder-utils", true);
+loader.lazyRequireGetter(this, "getKnownDeviceFront",
+  "devtools/shared/fronts/device", true);
 
 loader.lazyGetter(this, "domNodeConstants", () => {
   return require("devtools/shared/dom-node-constants");
@@ -2765,6 +2767,14 @@ Toolbox.prototype = {
       this._styleSheets = null;
     }
 
+    // Destroy the device front for the current client if any.
+    // A given DeviceFront instance can cached and shared between different panels, so
+    // destroying it is the responsibility of the toolbox.
+    let deviceFront = getKnownDeviceFront(this.target.client);
+    if (deviceFront) {
+      deviceFront.destroy();
+    }
+
     // Detach the thread
     detachThread(this._threadClient);
     this._threadClient = null;

devtools/shared/fronts/device.js

@@ -38,6 +38,17 @@ const DeviceFront = protocol.FrontClassWithSpec(deviceSpec, {
 
 const _knownDeviceFronts = new WeakMap();
 
+/**
+ * Retrieve the device front already created for the provided client, if available.
+ */
+exports.getKnownDeviceFront = function(client) {
+  return _knownDeviceFronts.get(client);
+};
+
+/**
+ * Only one DeviceFront is created for a given client, afterwards the instance is cached
+ * and returned immediately.
+ */
 exports.getDeviceFront = function(client, form) {
   if (!form.deviceActor) {
     return null;