Get sample_app running on Android again

Second try after first broke build
https://codereview.chromium.org/240003006/

TBR=viettrungluu
BUG=

Review URL: https://codereview.chromium.org/242973004

git-svn-id: http://src.chromium.org/svn/trunk/src/build@265070 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

android/adb_run_mojo_shell

@@ -8,7 +8,8 @@ if [ $# -gt 0 ] ; then
    INTENT_ARGS="-d \"$1\""  # e.g. a URL
 fi
 
-adb shell am start \
+adb logcat -c
+adb shell am start -S \
   -a android.intent.action.VIEW \
   -n org.chromium.mojo_shell_apk/.MojoShellActivity \
   $INTENT_ARGS