[DevTools] Extract platform module.

Source/devtools/front_end/host/ToolboxHost.js

Index: Source/devtools/front_end/host/ToolboxHost.js
diff --git a/Source/devtools/front_end/host/ToolboxHost.js b/Source/devtools/front_end/host/ToolboxHost.js
deleted file mode 100644
index 75e973fd3fc0843e7900d81e605abbba7760992d..0000000000000000000000000000000000000000
--- a/Source/devtools/front_end/host/ToolboxHost.js
+++ /dev/null
@@ -1,15 +0,0 @@
-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-/**
- * @interface
- */
-WebInspector.ToolboxHost = function() {}
-
-WebInspector.ToolboxHost.prototype = {
-    /**
-     * @param {!Document} document
-     */
-    toolboxLoaded: function(document) {}
-}