Android WebView: clean up the AwContentsClientBridge webcontents userdata.

android_webview/browser/aw_contents_client_bridge_base.h

Index: android_webview/browser/aw_contents_client_bridge_base.h
diff --git a/android_webview/browser/aw_contents_client_bridge_base.h b/android_webview/browser/aw_contents_client_bridge_base.h
index a24aa4bd9aaed578c8956c22fca0c8be5debf3e9..3bc18151990d32e2065166f98e83bf4d44fae9af 100644
--- a/android_webview/browser/aw_contents_client_bridge_base.h
+++ b/android_webview/browser/aw_contents_client_bridge_base.h
@@ -34,6 +34,7 @@ class AwContentsClientBridgeBase {
   // Adds the handler to the UserData registry.
   static void Associate(content::WebContents* web_contents,
                         AwContentsClientBridgeBase* handler);
+  static void Disassociate(content::WebContents* web_contents);
   static AwContentsClientBridgeBase* FromWebContents(
       content::WebContents* web_contents);
   static AwContentsClientBridgeBase* FromID(int render_process_id,