Improve adb_run_mojo_shell

BUG=None
R=abarth@chromium.org, abarth

Review URL: https://codereview.chromium.org/115893005

git-svn-id: http://src.chromium.org/svn/trunk/src/build@240921 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

android/adb_run_mojo_shell

@@ -8,7 +8,9 @@ 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
+adb logcat -s MojoShellApplication MojoShellActivity chromium