Add the main frame routing ID to WebContentsDelegate, use it in BackgroundContents.

components/web_contents_delegate_android/web_contents_delegate_android.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 "components/web_contents_delegate_android/web_contents_delegate_android.h"
 
 #include <android/keycodes.h>
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_array.h"
@@ skipping 210 matching lines @@
   JNIEnv* env = AttachCurrentThread();
   ScopedJavaLocalRef<jobject> obj = GetJavaDelegate(env);
   if (obj.is_null())
     return;
   Java_WebContentsDelegateAndroid_didNavigateToPendingEntry(env, obj.obj());
 }
 
 bool WebContentsDelegateAndroid::ShouldCreateWebContents(
     WebContents* web_contents,
     int route_id,
+    int main_frame_route_id,
     WindowContainerType window_container_type,
     const base::string16& frame_name,
     const GURL& target_url,
     const std::string& partition_id,
     content::SessionStorageNamespace* session_storage_namespace) {
   JNIEnv* env = AttachCurrentThread();
   ScopedJavaLocalRef<jobject> obj = GetJavaDelegate(env);
   if (obj.is_null())
     return true;
   ScopedJavaLocalRef<jstring> java_url =
@@ skipping 188 matching lines @@
 // Native JNI methods
 // ----------------------------------------------------------------------------
 
 // Register native methods
 
 bool RegisterWebContentsDelegateAndroid(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 }  // namespace web_contents_delegate_android