Apply theme to half sheet and clean up

https://screenshot.googleplex.com/67T5pt8gK7hLG4C

Test: Screenshot
Bug: 196262706
Change-Id: Ia4d55f7dfff49993222ac3627851ab89279b51d0
diff --git a/nearby/halfsheet/AndroidManifest.xml b/nearby/halfsheet/AndroidManifest.xml
index 3e8b39b..3df7970 100644
--- a/nearby/halfsheet/AndroidManifest.xml
+++ b/nearby/halfsheet/AndroidManifest.xml
@@ -15,17 +15,16 @@
   ~ limitations under the License.
   -->
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools"
     package="com.android.nearby.halfsheet">
-    <application android:label="@string/app_name">
+    <application>
         <activity
             android:name="com.android.nearby.halfsheet.HalfSheetActivity"
-            android:exported="true">
+            android:exported="true"
+            android:theme="@style/HalfSheetStyle" >
             <intent-filter>
                 <action android:name="android.nearby.SHOW_HALFSHEET"/>
                 <category android:name="android.intent.category.DEFAULT"/>
             </intent-filter>
         </activity>
     </application>
-
-</manifest>
\ No newline at end of file
+</manifest>