[First Run][Android] Change the animation at the end of the FRE

This CL changes the animation used for the transition from FRE activity
to the activity that has triggered the FRE - now fade-out/fade-in
transition is used instead of the default sliding transition. This looks
better (especially for dialog-based FRE) and allows code simplification
(no more need to disable the animation for TabbedModeFirstRunActivity).

Bug: 945284
Change-Id: I8ae9e7d32cef5115ce617455dc24b970d73c1aa0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1537113
Auto-Submit: Boris Sazonov <bsazonov@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Boris Sazonov <bsazonov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644520}

chrome/android/java/src/org/chromium/chrome/browser/firstrun/FirstRunActivityBase.java

@@ -116,6 +116,8 @@ public abstract class FirstRunActivityBase extends AsyncInitializationActivity {
             // Use the PendingIntent to send the intent that originally launched Chrome. The intent
             // will go back to the ChromeLauncherActivity, which will route it accordingly.
             pendingIntent.send(Activity.RESULT_OK, onFinished, null);
+            // Use fade-out animation for the transition from this activity so the original intent.
+            overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out);
             return true;
         } catch (CanceledException e) {
             Log.e(TAG, "Unable to send PendingIntent.", e);

chrome/android/java/src/org/chromium/chrome/browser/firstrun/FreIntentCreator.java

@@ -87,11 +87,6 @@ public class FreIntentCreator {
         final Class<?> activityClass;
         if (shouldSwitchToTabbedMode(context)) {
             activityClass = TabbedModeFirstRunActivity.class;
-
-            // Going to launch TabbedModeFRE. Have to disable animation on the intent launched after
-            // the FRE is completed to make the transition seamless.
-            intentToLaunchAfterFreComplete = new Intent(intentToLaunchAfterFreComplete);
-            intentToLaunchAfterFreComplete.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
         } else {
             activityClass = FirstRunActivity.class;
         }