Cancel handler for JS unload handler prevents hang.

 Bug 6803309
 When the alert dialog raised by the JS unload handler was pressed
 outside the alert region, it was canceled and no response was
 sent back to WebViewCore. This captures the cancel event so that
 WebViewCore doesn't hang.

Change-Id: I0c125e759a252a803c2c77aa9533adef7fa82d3d

Author: George Mount

core/java/android/webkit/CallbackProxy.java

@@ -736,6 +736,14 @@ public void onClick(
                                                 res.cancel();
                                             }
                                         })
+                                .setOnCancelListener(
+                                        new DialogInterface.OnCancelListener() {
+                                            @Override
+                                            public void onCancel(
+                                                    DialogInterface dialog) {
+                                                res.cancel();
+                                            }
+                                        })
                                 .show();
                     }
                     receiver.setReady();