[Payments] Add integration test for canceling editor by clicking Android back button

chrome/android/javatests/src/org/chromium/chrome/browser/payments/PaymentRequestTestBase.java

 // Copyright 2016 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.payments;
 
 import static java.util.Arrays.asList;
 
 import android.os.Handler;
+import android.view.KeyEvent;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.CheckBox;
 import android.widget.EditText;
 import android.widget.Spinner;
 
 import org.chromium.base.ThreadUtils;
 import org.chromium.base.test.util.CallbackHelper;
 import org.chromium.base.test.util.RetryOnFailure;
 import org.chromium.base.test.util.UrlUtils;
@@ skipping 254 matching lines @@
         int callCount = helper.getCallCount();
         ThreadUtils.runOnUiThreadBlocking(new Runnable() {
             @Override
             public void run() {
                 mUI.getEditorView().findViewById(resourceId).performClick();
             }
         });
         helper.waitForCallback(callCount);
     }
 
+    protected void clickAndroidBackButtonInEditorAndWait(CallbackHelper helper)
+            throws InterruptedException, TimeoutException {
+        int callCount = helper.getCallCount();
+        ThreadUtils.runOnUiThread(new Runnable() {
+            @Override
+            public void run() {
+                mUI.getEditorView().dispatchKeyEvent(
+                        new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_BACK));
+                mUI.getEditorView().dispatchKeyEvent(
+                        new KeyEvent(KeyEvent.ACTION_UP, KeyEvent.KEYCODE_BACK));
+            }
+        });
+        helper.waitForCallback(callCount);
+    }
+
     /** Clicks on a button in the card unmask UI. */
     protected void clickCardUnmaskButtonAndWait(final int dialogButtonId, CallbackHelper helper)
             throws InterruptedException, TimeoutException {
         int callCount = helper.getCallCount();
         ThreadUtils.runOnUiThreadBlocking(new Runnable() {
             @Override
             public void run() {
                 mCardUnmaskPrompt.getDialogForTest().getButton(dialogButtonId).performClick();
             }
         });
@@ skipping 668 matching lines @@
                 List<PaymentItem> displayItems, Map<String, PaymentDetailsModifier> modifiers,
                 InstrumentDetailsCallback detailsCallback) {
             detailsCallback.onInstrumentDetailsReady(
                     mMethodName, "{\"transaction\": 1337}");
         }
 
         @Override
         public void dismissInstrument() {}
     }
 }