Use a resource throttle to implement shouldOverrideUrlLoading.

android_webview/browser/renderer_host/aw_resource_dispatcher_host_delegate.cc

 // 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.
 
 #include "android_webview/browser/renderer_host/aw_resource_dispatcher_host_delegate.h"
 
 #include <string>
 
 #include "android_webview/browser/aw_contents_io_thread_client.h"
 #include "android_webview/browser/aw_login_delegate.h"
@@ skipping 208 matching lines @@
       content::ResourceRequestInfo::ForRequest(request);
 
   // We always push the throttles here. Checking the existence of io_client
   // is racy when a popup window is created. That is because RequestBeginning
   // is called whether or not requests are blocked via BlockRequestForRoute()
   // however io_client may or may not be ready at the time depending on whether
   // webcontents is created.
   throttles->push_back(new IoThreadClientThrottle(
       request_info->GetChildID(), request_info->GetRenderFrameID(), request));
 
-  // We allow intercepting only navigations within main frames. This
-  // is used to post onPageStarted. We handle shouldOverrideUrlLoading
-  // via a sync IPC.
-  if (resource_type == content::RESOURCE_TYPE_MAIN_FRAME) {
+  if (resource_type == content::RESOURCE_TYPE_MAIN_FRAME ||
+      (resource_type == content::RESOURCE_TYPE_SUB_FRAME &&
+       !request->url().SchemeIs(url::kHttpScheme) &&
+       !request->url().SchemeIs(url::kHttpsScheme) &&
+       !request->url().SchemeIs(url::kAboutScheme))) {
     throttles->push_back(InterceptNavigationDelegate::CreateThrottleFor(
         request));
   } else {
     InterceptNavigationDelegate::UpdateUserGestureCarryoverInfo(request);

[sgurun-gerrit only, 2015/07/08 01:08:54]

so we do not enter updateusergesturecarryoverinfo for subframes any more. this
sounds wrong to me, can you confirm it is correct here.

[gsennton, 2015/07/08 11:12:55]

Right, I should have spotted this :(. So instead of

} else {
   InterceptNavigationDelegate::UpdateUserGestureCarryoverInfo(request);
}

we should use the following?

}
if (resource_type != content::RESOURCE_TYPE_MAIN_FRAME)
    InterceptNavigationDelegate::UpdateUserGestureCarryoverInfo(request);


cc'ing jaekyun@ who added the UserGestureCarryOver flag.

[Jaekyun Seok (inactive), 2015/07/08 21:26:18]

The latter seems correct.

But is this to handle external protocol in subframe? In Chrome, we use
ExternalProtocolHandler for the purpose instead;
https://codereview.chromium.org/1091253008/.

Can we use the same logic here?

[gsennton, 2015/07/09 12:53:48]

This is to call the shouldOverrideUrlLoading callback letting the owning
application decide whether it wants to override the navigation, i.e. make
WebView ignore it (and then the application can do whatever it wants to do with
the url).

Why doesn't the resource throttle used in chrome work for subframes (which the
commit message says in the CL you linked to) and why does the external protocol
handler work instead? AFAICT shouldOverrideUrlLoading is being called on
subframes for WebView with this Cl, is there any specific reason for using the
ExternalProtocolHandler path/logic?

[Jaekyun Seok (inactive), 2015/07/09 20:33:58]

InterceptNavigationDelegate#ShouldIgnoreNavigation is called eventually when
ExternalProtocolHandler is used;
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/ui/....
So both are identical.
(CCed qinmin@ for more details)

As I know, historically InterceptNavigationResourceThrottle is being used only
for mainframe and it handles not only external protocols but also internal ones.
And ExternalProtocolHandler is to handle only external protocols, and so in the
CL it was used for external protocols from subframe.

And InterceptNavigationResourceThrottle always sets true as
NavigationParams.is_main_frame;
https://code.google.com/p/chromium/codesearch#chromium/src/components/navigat...
So you couldn't use InterceptNavigationResourceThrottle as it is anyway.

   }
 }
 
 void AwResourceDispatcherHostDelegate::OnRequestRedirected(
     const GURL& redirect_url,
     net::URLRequest* request,
     content::ResourceContext* resource_context,
     content::ResourceResponse* response) {
   AddExtraHeadersIfNeeded(request, resource_context);
 }
@@ skipping 196 matching lines @@
       net::HttpRequestHeaders headers;
       headers.AddHeadersFromString(extra_headers);
       for (net::HttpRequestHeaders::Iterator it(headers); it.GetNext(); ) {
         request->SetExtraRequestHeaderByName(it.name(), it.value(), false);
       }
     }
   }
 }
 
 }  // namespace android_webview