[DevTools] Extract part of DevTools into inspector app.

Source/devtools/front_end/host/InspectorFrontendHost.js

Index: Source/devtools/front_end/host/InspectorFrontendHost.js
diff --git a/Source/devtools/front_end/host/InspectorFrontendHost.js b/Source/devtools/front_end/host/InspectorFrontendHost.js
index e51e3c3405e98b01051866ecb7d0bebb1d3a66fe..bcacc062565f579163c07194eab0f7ea36ac7d7d 100644
--- a/Source/devtools/front_end/host/InspectorFrontendHost.js
+++ b/Source/devtools/front_end/host/InspectorFrontendHost.js
@@ -628,6 +628,10 @@ WebInspector.InspectorFrontendHostStub.prototype = {
 var InspectorFrontendHost = window.InspectorFrontendHost || null;
 
 (function() {
+    if (window.top) {
+        // FIXME(dgozman): use InspectorAppHost everywhere in inspector app instead of InspectorFrontendHost.
+        InspectorFrontendHost = window.top.InspectorFrontendHost || null;
+    }
     if (!InspectorFrontendHost) {
         // Instantiate stub for web-hosted mode if necessary.
         InspectorFrontendHost = new WebInspector.InspectorFrontendHostStub();