Use a resource throttle to implement shouldOverrideUrlLoading.

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

Index: android_webview/java/src/org/chromium/android_webview/AwWebContentsObserver.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwWebContentsObserver.java b/android_webview/java/src/org/chromium/android_webview/AwWebContentsObserver.java
index 85cf90ce03c7c53559c978b64724d96c045e606f..53715c67b5f8c6d520ee8ec445e1054c31c8abbc 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwWebContentsObserver.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwWebContentsObserver.java
@@ -53,9 +53,13 @@ public class AwWebContentsObserver extends WebContentsObserver {
         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);
         }
     }