Bug 1539979 - Create toolbox iframe for Window host with helper;r=bgrins

Depends on D26316
Instead of using a hardcoded iframe in toolbox-window.xul, reuse the same helper as for the other hosts.
Will facilitate switching to type="content".

Differential Revision: https://phabricator.services.mozilla.com/D26317

--HG--
extra : moz-landing-system : lando

devtools/client/framework/test/browser_toolbox_hosts.js

@@ -84,7 +84,7 @@ async function testWindowHost() {
   const win = Services.wm.getMostRecentWindow("devtools:toolbox");
   ok(win, "toolbox separate window exists");
 
-  const iframe = win.document.getElementById("toolbox-iframe");
+  const iframe = win.document.querySelector(".devtools-toolbox-window-iframe");
   checkToolboxLoaded(iframe);
 }
 

devtools/client/framework/toolbox-hosts.js

@@ -249,8 +249,15 @@ WindowHost.prototype = {
         win.removeEventListener("load", frameLoad, true);
         win.focus();
 
-        this.frame = win.document.getElementById("toolbox-iframe");
-        this.emit("ready", this.frame);
+        this.frame = createDevToolsFrame(win.document, "devtools-toolbox-window-iframe");
+        win.document.getElementById("devtools-toolbox-window").appendChild(this.frame);
+
+        // The forceOwnRefreshDriver attribute is set to avoid Windows only issues with
+        // CSS transitions when switching from docked to window hosts.
+        // Added in Bug 832920, should be reviewed in Bug 1542468.
+        this.frame.setAttribute("forceOwnRefreshDriver", "");
+
+        this.frame.setAttribute("src", "about:blank");
         resolve(this.frame);
       };
 

devtools/client/framework/toolbox-window.xul

@@ -14,5 +14,4 @@
         width="900" height="320"
         persist="screenX screenY width height sizemode">
   <tooltip id="aHTMLTooltip" page="true"/>
-  <iframe id="toolbox-iframe" flex="1" forceOwnRefreshDriver="" tooltip="aHTMLTooltip"></iframe>
 </window>