Signin: Reuse existing "update gms" dialogs when possible.

chrome/android/java/src/org/chromium/chrome/browser/externalauth/UserRecoverableErrorHandler.java

 // Copyright 2015 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.chrome.browser.externalauth;
 
 import android.app.Activity;
 import android.app.Dialog;
 import android.content.Context;
 
@@ skipping 120 matching lines @@
          * The modal dialog that is shown to the user.
          */
         private Dialog mDialog;
 
         /**
          * Whether the dialog can be canceled by the user.
          */
         private final boolean mCancelable;
 
         /**
+         * Last error code from Google Play Services.
+         */
+        private int mErrorCode;
+
+        /**
          * Create a new Modal Dialog handler for the specified activity and error code. The
          * specified activity may be used to launch the dialog via
          * {@link Activity#startActivityForResult(android.content.Intent, int)} and also to receive
          * the result via Activity's protected onActivityResult method.
          *
          * @param activity the activity to use
          * @param cancelable whether the dialog can be canceled by the user
          */
         public ModalDialog(Activity activity, boolean cancelable) {
             mActivity = activity;
             mCancelable = cancelable;
         }
 
         /**
          * Displays the dialog in a modal manner using
          * {@link GoogleApiAvailability#getErrorDialog(Activity, int, int)}.
          * @param context the context in which the error was encountered
          * @param errorCode the error code from Google Play Services
          */
         @Override
         protected final void handle(final Context context, final int errorCode) {
-            mDialog = GoogleApiAvailability.getInstance().getErrorDialog(
-                    mActivity, errorCode, NO_RESPONSE_REQUIRED);
+            // Assume old dialogs generated by the same error handler are obsolete when an error
+            // with a different error code is encountered.
+            if (mErrorCode != errorCode) {
+                cancelDialog();
+            }
+            if (mDialog == null) {
+                mDialog = GoogleApiAvailability.getInstance().getErrorDialog(
+                        mActivity, errorCode, NO_RESPONSE_REQUIRED);
+                mErrorCode = errorCode;
+            }
             // This can happen if |errorCode| is ConnectionResult.SERVICE_INVALID.
             if (mDialog != null) {
                 mDialog.setCancelable(mCancelable);
                 mDialog.show();
             }
             sErrorHandlerActionHistogramSample.record(ERROR_HANDLER_ACTION_MODAL_DIALOG);
         }
 
         /**
          * Cancels the dialog.
          */
         public void cancelDialog() {
             if (mDialog != null) {
                 mDialog.cancel();
+                mDialog = null;
             }
         }
     }
 }