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

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

Index: chrome/android/javatests/src/org/chromium/chrome/browser/payments/PaymentRequestTestBase.java
diff --git a/chrome/android/javatests/src/org/chromium/chrome/browser/payments/PaymentRequestTestBase.java b/chrome/android/javatests/src/org/chromium/chrome/browser/payments/PaymentRequestTestBase.java
index c061c3520eb5a1657e3b0383e9ba36ecb9a48c01..9ad1f91c7f86b1e3106f747ff22d740377646505 100644
--- a/chrome/android/javatests/src/org/chromium/chrome/browser/payments/PaymentRequestTestBase.java
+++ b/chrome/android/javatests/src/org/chromium/chrome/browser/payments/PaymentRequestTestBase.java
@@ -7,6 +7,7 @@ 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;
@@ -281,6 +282,21 @@ abstract class PaymentRequestTestBase extends ChromeActivityTestCaseBase<ChromeT
         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 {