[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..0cb1c67a226f64dfba5bf03282d495a10a53d2ec 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 +282,22 @@ 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));
+            }
+        });
+        getInstrumentation().waitForIdleSync();

[please use gerrit instead, 2017/02/21 19:33:08]

Why is this line necessary in this method? It's not used in the other helper
methods. I though helper.waitForCallback(callCount) should be sufficient.

[gogerald1, 2017/02/21 20:44:03]

Done.

+        helper.waitForCallback(callCount);
+    }
+
     /** Clicks on a button in the card unmask UI. */
     protected void clickCardUnmaskButtonAndWait(final int dialogButtonId, CallbackHelper helper)
             throws InterruptedException, TimeoutException {