[aw] Unregister delegates from AwContents.destroy()

android_webview/native/aw_contents.cc

Index: android_webview/native/aw_contents.cc
diff --git a/android_webview/native/aw_contents.cc b/android_webview/native/aw_contents.cc
index f90241875cf5bd240fdedcf313a363ae0943cbab..6be0974420ccb9773a0b7fb20eb3e304448e602d 100644
--- a/android_webview/native/aw_contents.cc
+++ b/android_webview/native/aw_contents.cc
@@ -300,6 +300,10 @@ void AwContents::Destroy(JNIEnv* env, jobject obj) {
   AwContentsClientBridgeBase::Disassociate(web_contents_.get());
   contents_client_bridge_.reset();
 
+  // Do not wait until the WebContents are deleted asynchronously to clear
+  // the delegate and stop sending callbacks.
+  web_contents_->SetDelegate(NULL);
+
   // We do not delete AwContents immediately. Some applications try to delete
   // Webview in ShouldOverrideUrlLoading callback, which is a sync IPC from
   // Webkit.