TileBenchmark test app needs read sdcard permission

Since the app is using JB API level, it's required to declare
an explicit READ_EXTERNAL_STORAGE permission

Change-Id: I84142d51aeab4bc28269a6fea716c8663e080118

Author: guang-google

tests/TileBenchmark/AndroidManifest.xml

@@ -3,6 +3,7 @@
       android:versionCode="1"
       android:versionName="1.0" package="com.test.tilebenchmark">
     <uses-permission android:name="android.permission.INTERNET"/>
+    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
     <application android:icon="@drawable/icon"
                  android:label="@string/app_name"
                  android:hardwareAccelerated="true">