Use a resource throttle to implement shouldOverrideUrlLoading.

android_webview/common/render_view_messages.h

 // Copyright (c) 2012 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.
 
 // Multiply-included file, no traditional include guard.
 #include "android_webview/common/aw_hit_test_data.h"
 #include "content/public/common/common_param_traits.h"
 #include "ipc/ipc_channel_handle.h"
 #include "ipc/ipc_message_macros.h"
 #include "ipc/ipc_platform_file.h"
@@ skipping 80 matching lines @@
                     android_webview::AwHitTestData)
 
 // Sent whenever the page scale factor (as seen by RenderView) is changed.
 IPC_MESSAGE_ROUTED1(AwViewHostMsg_PageScaleFactorChanged,
                     float /* page_scale_factor */)
 
 // Sent whenever the contents size (as seen by RenderView) is changed.
 IPC_MESSAGE_ROUTED1(AwViewHostMsg_OnContentsSizeChanged,
                     gfx::Size /* contents_size */)
 
-// Sent immediately before a top level navigation is initiated within Blink.
-// There are some exlusions, the most important ones are it is not sent
-// when creating a popup window, and not sent for application initiated
-// navigations. See AwContentRendererClient::HandleNavigation for all
-// cornercases. This is sent before updating the NavigationController state
-// or creating a URLRequest for the main frame resource.
-IPC_SYNC_MESSAGE_CONTROL4_1(AwViewHostMsg_ShouldOverrideUrlLoading,
-                            int /* render_frame_id id */,
-                            base::string16 /* in - url */,
-                            bool /* in - has_user_gesture */,
-                            bool /* in - is_redirect */,
-                            bool /* out - result */)
-
 // Sent when a subframe is created.
 IPC_MESSAGE_CONTROL2(AwViewHostMsg_SubFrameCreated,
                      int /* parent_render_frame_id */,
                      int /* child_render_frame_id */)