[Signin][Android] Use 'Turn on sync' as button text in promo

Changes the text used for the primary button in sync promo that is shown
in the signed out state. The text is changed from "Continue as ..." to
"Turn on sync". Applied only if MobileIdentityConsistency flag is
enabled.

Screenshot: https://crbug.com/1136905#c1.

Bug: 1136905
Change-Id: I967768061e26a01a4d34cdedee463fd8276dc969
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2462267
Commit-Queue: Boris Sazonov <bsazonov@chromium.org>
Reviewed-by: Tanmoy Mollik <triploblastic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816526}

chrome/android/java/src/org/chromium/chrome/browser/signin/SigninPromoController.java

@@ -271,7 +271,11 @@ public class SigninPromoController {
 
         view.getDescription().setText(mDescriptionStringIdNoAccount);
 
+        if (ChromeFeatureList.isEnabled(ChromeFeatureList.MOBILE_IDENTITY_CONSISTENCY)) {
+            view.getPrimaryButton().setText(R.string.sync_promo_turn_on_sync);
+        } else {
             view.getPrimaryButton().setText(R.string.sign_in_to_chrome);
+        }
         view.getPrimaryButton().setOnClickListener(v -> signinWithNewAccount(context));
 
         view.getSecondaryButton().setVisibility(View.GONE);
@@ -284,9 +288,13 @@ public class SigninPromoController {
 
         view.getDescription().setText(mDescriptionStringId);
 
-        String signinButtonText = context.getString(
-                R.string.signin_promo_continue_as, mProfileData.getGivenNameOrFullNameOrEmail());
+        if (ChromeFeatureList.isEnabled(ChromeFeatureList.MOBILE_IDENTITY_CONSISTENCY)) {
+            view.getPrimaryButton().setText(R.string.sync_promo_turn_on_sync);
+        } else {
+            String signinButtonText = context.getString(R.string.signin_promo_continue_as,
+                    mProfileData.getGivenNameOrFullNameOrEmail());
             view.getPrimaryButton().setText(signinButtonText);
+        }
         view.getPrimaryButton().setOnClickListener(v -> signinWithDefaultAccount(context));
 
         view.getSecondaryButton().setText(R.string.signin_promo_choose_another_account);