YogaLayout perf tests

Summary: We would like to know some numbers on benchmarking `YogaLayout` against other layouts, particularly `LinearLayout`.  This implements a `BenchmarkActivity` to fill that need.

Reviewed By: emilsjolander

Differential Revision: D4565531

fbshipit-source-id: fe1c558beb603c3116ac3d0dd6654b0376dd6b8a

android/sample/AndroidManifest.xml

@@ -22,6 +22,8 @@
     android:targetSdkVersion="19"
     />
 
+  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
+
   <application
       android:label="@string/app_name"
       android:icon="@drawable/ic_launcher"
@@ -42,6 +44,11 @@
 
     </activity>
 
+    <activity
+        android:name=".BenchmarkActivity"
+        android:exported="false"
+        />
+
   </application>
 
 </manifest>