Add AX ID for Cancel and Done button on Translate Language Picker.

Currently, the test uses the following matchers to find the cancel and
done button on language picker:

grey_allOf(chrome_test_util::ButtonWithAccessibilityLabel(@"Cancel"),
                    grey_userInteractionEnabled(), nil);

This is not bullet proof and may break any time, and this CL fixes the
issue by adding AX ID to both the cancel and done buttons.

Bug: 750344
Change-Id: I4fda45961b684b877adf29a5bf0fee6e03f1ba8d
Reviewed-on: https://chromium-review.googlesource.com/594831Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Yuke Liao <liaoyuke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490840}

ios/chrome/browser/translate/before_translate_infobar_controller.h

@@ -7,6 +7,12 @@
 
 #include "ios/chrome/browser/infobars/infobar_controller.h"
 
+// The accessibility identifier of the cancel button on language picker view.
+extern NSString* const kLanguagePickerCancelButtonId;
+
+// The accessibility identifier of the done button on language picker view.
+extern NSString* const kLanguagePickerDoneButtonId;
+
 @interface BeforeTranslateInfoBarController : InfoBarController
 
 @end

ios/chrome/browser/translate/before_translate_infobar_controller.mm

@@ -22,6 +22,9 @@
 #error "This file requires ARC support."
 #endif
 
+NSString* const kLanguagePickerCancelButtonId = @"LanguagePickerCancelButton";
+NSString* const kLanguagePickerDoneButtonId = @"LanguagePickerDoneButton";
+
 namespace {
 
 CGFloat kNavigationBarHeight = 44;
@@ -302,10 +305,12 @@ NSTimeInterval kPickerAnimationDurationInSeconds = 0.2;
       initWithBarButtonSystemItem:UIBarButtonSystemItemDone
                            target:self
                            action:@selector(languageSelectionDone)];
+  [doneButton setAccessibilityIdentifier:kLanguagePickerDoneButtonId];
   UIBarButtonItem* cancelButton = [[UIBarButtonItem alloc]
       initWithBarButtonSystemItem:UIBarButtonSystemItemCancel
                            target:self
                            action:@selector(dismissLanguageSelectionView)];
+  [cancelButton setAccessibilityIdentifier:kLanguagePickerCancelButtonId];
   UINavigationItem* item = [[UINavigationItem alloc] initWithTitle:@""];
   [item setRightBarButtonItem:doneButton];
   [item setLeftBarButtonItem:cancelButton];

ios/chrome/browser/translate/translate_egtest.mm

@@ -19,6 +19,7 @@
 #import "components/translate/ios/browser/js_translate_manager.h"
 #import "components/translate/ios/browser/language_detection_controller.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
+#include "ios/chrome/browser/translate/before_translate_infobar_controller.h"
 #include "ios/chrome/browser/translate/chrome_ios_translate_client.h"
 #import "ios/chrome/test/app/chrome_test_util.h"
 #import "ios/chrome/test/app/tab_test_util.h"
@@ -107,20 +108,6 @@ NSString* GetTranslateInfobarSwitchLabel(const std::string& language) {
       IDS_TRANSLATE_INFOBAR_ALWAYS_TRANSLATE, base::UTF8ToUTF16(language)));
 }
 
-// Returns a matcher for the button with label "Cancel" in the language picker.
-// TODO(crbug.com/750344): Change the matcher to use accessibility ID.
-id<GREYMatcher> LanguagePickerCancelButton() {
-  return grey_allOf(chrome_test_util::ButtonWithAccessibilityLabel(@"Cancel"),
-                    grey_userInteractionEnabled(), nil);
-}
-
-// Returns a matcher for the button with label "Done" in the language picker.
-// TODO(crbug.com/750344): Change the matcher to use accessibility ID.
-id<GREYMatcher> LanguagePickerDoneButton() {
-  return grey_allOf(chrome_test_util::ButtonWithAccessibilityLabel(@"Done"),
-                    grey_userInteractionEnabled(), nil);
-}
-
 #pragma mark - TestResponseProvider
 
 // A ResponseProvider that provides html responses of texts in different
@@ -615,9 +602,8 @@ using translate::LanguageDetectionController;
       selectElementWithMatcher:chrome_test_util::ButtonWithAccessibilityLabel(
                                    kFrench)] performAction:grey_tap()];
 
-  // The language picker uses the system accessibility labels (thus no
-  // IDS_CANCEL here).
-  [[EarlGrey selectElementWithMatcher:LanguagePickerCancelButton()]
+  [[EarlGrey selectElementWithMatcher:grey_accessibilityID(
+                                          kLanguagePickerCancelButtonId)]
       assertWithMatcher:grey_notNil()];
 
   // Change the language using the picker.
@@ -628,7 +614,8 @@ using translate::LanguageDetectionController;
   [[EarlGrey selectElementWithMatcher:languageMatcher]
       performAction:grey_tap()];
 
-  [[EarlGrey selectElementWithMatcher:LanguagePickerDoneButton()]
+  [[EarlGrey selectElementWithMatcher:grey_accessibilityID(
+                                          kLanguagePickerDoneButtonId)]
       performAction:grey_tap()];
   [[EarlGrey
       selectElementWithMatcher:chrome_test_util::ButtonWithAccessibilityLabel(