Remove usages of ActionBarActivity.

ActionBarActivity has been deprecated for 2+ years and has been
extending AppCompatActivity for all that time. These changes
should be no-ops.

Bug: 35253513
Test: None
Change-Id: I969a612d4ae59d26369fea011608279423d30038
diff --git a/JustForUs/justforus/src/main/java/com/example/android/justforus/MainActivity.java b/JustForUs/justforus/src/main/java/com/example/android/justforus/MainActivity.java
index d799f30..fd836be 100644
--- a/JustForUs/justforus/src/main/java/com/example/android/justforus/MainActivity.java
+++ b/JustForUs/justforus/src/main/java/com/example/android/justforus/MainActivity.java
@@ -21,7 +21,7 @@
 import android.net.Uri;
 import android.os.Bundle;
 import android.support.v4.app.ShareCompat;
-import android.support.v7.app.ActionBarActivity;
+import android.support.v7.app.AppCompatActivity;
 import android.text.TextUtils;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -45,7 +45,7 @@
  * <p>Tapping on a coupon to redeem it brings up the Android "share"
  * dialog with a pre-populated message based on the coupon text.
  */
-public class MainActivity extends ActionBarActivity implements OnItemClickListener {
+public class MainActivity extends AppCompatActivity implements OnItemClickListener {
 
     // Name of person giving out these coupons. When the user clicks on a coupon and shares
     // to another app, this name will be part of the pre-populated text.