Use a resource throttle to implement shouldOverrideUrlLoading.

android_webview/java/src/org/chromium/android_webview/AwWebContentsObserver.java

 // Copyright 2014 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.
 
 package org.chromium.android_webview;
 
 import org.chromium.android_webview.AwContents.VisualStateCallback;
 import org.chromium.base.ThreadUtils;
 import org.chromium.content_public.browser.WebContents;
 import org.chromium.content_public.browser.WebContentsObserver;
@@ skipping 35 matching lines @@
     }
 
     @Override
     public void didFailLoad(boolean isProvisionalLoad, boolean isMainFrame, int errorCode,
             String description, String failingUrl, boolean wasIgnoredByHandler) {
         AwContentsClient client = mAwContentsClient.get();
         if (client == null) return;
         String unreachableWebDataUrl = AwContentsStatics.getUnreachableWebDataUrl();
         boolean isErrorUrl =
                 unreachableWebDataUrl != null && unreachableWebDataUrl.equals(failingUrl);
-        if (isMainFrame && !isErrorUrl && errorCode == NetError.ERR_ABORTED) {
+        if (isMainFrame && !isErrorUrl && errorCode == NetError.ERR_ABORTED
+                && !wasIgnoredByHandler) {
             // Need to call onPageFinished for backwards compatibility with the classic webview.
             // See also AwContents.IoThreadClientImpl.onReceivedError.
+            // If the navigation was ignored because of shouldOverrideUrlLoading we have already
+            // called onPageFinished in
+            // AwContents.InterceptNavigationDelegateImpl.shouldIgnoreNavigation instead.
             client.getCallbackHelper().postOnPageFinished(failingUrl);
         }
     }
 
     @Override
     public void didNavigateMainFrame(final String url, String baseUrl,
             boolean isNavigationToDifferentPage, boolean isFragmentNavigation, int statusCode) {
         // Only invoke the onPageCommitVisible callback when navigating to a different page,
         // but not when navigating to a different fragment within the same page.
         if (isNavigationToDifferentPage) {
@@ skipping 30 matching lines @@
         mCommittedNavigation = true;
         final AwContentsClient client = mAwContentsClient.get();
         if (client == null) return;
         client.getCallbackHelper().postDoUpdateVisitedHistory(url, isReload);
     }
 
     public boolean didEverCommitNavigation() {
         return mCommittedNavigation;
     }
 }