Revert of Remove the is_loading_ field from WebContentsImpl

content/common/frame_messages.h

 // Copyright 2013 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.
 
 // IPC messages for interacting with frames.
 // Multiply-included message file, hence no include guard.
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 898 matching lines @@
 
 // Notifies the browser that a document has been loaded.
 IPC_MESSAGE_ROUTED0(FrameHostMsg_DidFinishDocumentLoad)
 
 IPC_MESSAGE_ROUTED4(FrameHostMsg_DidFailLoadWithError,
                     GURL /* validated_url */,
                     int /* error_code */,
                     base::string16 /* error_description */,
                     bool /* was_ignored_by_handler */)
 
+// Sent when the renderer decides to ignore a navigation.
+IPC_MESSAGE_ROUTED0(FrameHostMsg_DidDropNavigation)
+
 // Sent when the renderer starts loading the page. |to_different_document| will
 // be true unless the load is a fragment navigation, or triggered by
 // history.pushState/replaceState.
 IPC_MESSAGE_ROUTED1(FrameHostMsg_DidStartLoading,
                     bool /* to_different_document */)
 
 // Sent when the renderer is done loading a page.
 IPC_MESSAGE_ROUTED0(FrameHostMsg_DidStopLoading)
 
 // Notifies the browser that this frame has new session history information.
@@ skipping 497 matching lines @@
 IPC_MESSAGE_ROUTED3(FrameHostMsg_FindMatchRects_Reply,
                     int /* version */,
                     std::vector<gfx::RectF> /* rects */,
                     gfx::RectF /* active_rect */)
 #endif
 
 // Adding a new message? Stick to the sort order above: first platform
 // independent FrameMsg, then ifdefs for platform specific FrameMsg, then
 // platform independent FrameHostMsg, then ifdefs for platform specific
 // FrameHostMsg.