Use a resource throttle to implement shouldOverrideUrlLoading.

android_webview/common/render_view_messages.h

Index: android_webview/common/render_view_messages.h
diff --git a/android_webview/common/render_view_messages.h b/android_webview/common/render_view_messages.h
index c2253d0d474e8bef2c2f0c36fe018824030c0b85..2e0211b41e9c30b75cdee5e586f6140bb9c4e519 100644
--- a/android_webview/common/render_view_messages.h
+++ b/android_webview/common/render_view_messages.h
@@ -98,17 +98,6 @@ IPC_MESSAGE_ROUTED1(AwViewHostMsg_PageScaleFactorChanged,
 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_CONTROL2_1(AwViewHostMsg_ShouldOverrideUrlLoading,
-                            int /* render_frame_id id */,
-                            base::string16 /* in - url */,
-                            bool /* out - result */)
-
 // Sent when a subframe is created.
 IPC_MESSAGE_CONTROL2(AwViewHostMsg_SubFrameCreated,
                      int /* parent_render_frame_id */,