[android_webview] Enable navigation interception for iframes.

android_webview/browser/renderer_host/aw_resource_dispatcher_host_delegate.cc

Index: android_webview/browser/renderer_host/aw_resource_dispatcher_host_delegate.cc
diff --git a/android_webview/browser/renderer_host/aw_resource_dispatcher_host_delegate.cc b/android_webview/browser/renderer_host/aw_resource_dispatcher_host_delegate.cc
index b24eb2b56eac50e61bccdadb308a07a74515d6c0..328cecf30f5e2d69e86b84336118844603d64e20 100644
--- a/android_webview/browser/renderer_host/aw_resource_dispatcher_host_delegate.cc
+++ b/android_webview/browser/renderer_host/aw_resource_dispatcher_host_delegate.cc
@@ -130,7 +130,22 @@ void AwResourceDispatcherHostDelegate::RequestBeginning(
   throttles->push_back(new MaybeCancelResourceThrottle(
       child_id, route_id, request));
 
-  if (resource_type == ResourceType::MAIN_FRAME) {
+  bool allow_intercepting =
+      // We ignore POST requests because of BUG=155250.
+      request->method() != "POST" &&
+      // We allow intercepting navigations within subframes, but only if the
+      // scheme other than http or https. This is because the embedder
+      // can't distinguish main frame and subframe callbacks (which could lead
+      // to broken content if the embedder decides to not ignore the main frame
+      // navigation, but ignores the subframe navigation).
+      // The reason this is supported at all is that certain JavaScript-based
+      // frameworks use iframe navigation as a form of communication with the
+      // embedder.
+      (resource_type == ResourceType::MAIN_FRAME ||
+       (resource_type == ResourceType::SUB_FRAME &&
+        !request->url().SchemeIs(chrome::kHttpScheme) &&
+        !request->url().SchemeIs(chrome::kHttpsScheme)));
+  if (allow_intercepting) {
     throttles->push_back(InterceptNavigationDelegate::CreateThrottleFor(
         request));
   }