Support running Viewer via android_gdb_app

platform_tools/android/bin/android_gdb_app

 #!/bin/bash
 #
 # android_gdb_app: Pushes gdbserver, launches sampleApp, and connects
 # the debugging environment.
 
 SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 source $SCRIPT_DIR/android_setup.sh "$@"
+source $SCRIPT_DIR/utils/setup_adb.sh
 
-APP_NAME=${APP_ARGS[0]}
+app=${APP_ARGS[0]}
+if [[ ${app} == '-'* ]]; then
+    echo "Defaulting to running SampleApp."
+    app="SampleApp"
+    APP_ARGS=( "SampleApp" ${APP_ARGS[*]} )
+fi
 PORT=5039
 
-source $SCRIPT_DIR/utils/setup_adb.sh
-
+if [[ ${app} == 'SampleApp' ]]; then
+    activity="com.skia.sample_app/com.skia.SkiaSampleActivity"
+    activityShort="com.skia.sample_app"
+elif [[ ${app} == "Viewer" ]] ; then
+    activity="org.skia.viewer/org.skia.viewer.ViewerActivity"
+    activityShort="org.skia.viewer"
+else
+    echo "ERROR: supports either 'SampleApp' or 'Viewer' as valid apps"
+    exit 1
+fi
 
 # Forward local to remote socket connection.
 $ADB $DEVICE_SERIAL forward "tcp:$PORT" "tcp:$PORT"
 
 # We kill all previous instances of gdbserver to rid all port overriding errors.
 if [ $(uname) == "Linux" ]; then
     $ADB $DEVICE_SERIAL shell ps | grep gdbserver | awk '{print $2}' | xargs -r $ADB $DEVICE_SERIAL shell kill
 elif [ $(uname) == "Darwin" ]; then
     $ADB $DEVICE_SERIAL shell ps | grep gdbserver | awk '{print $2}' | xargs $ADB $DEVICE_SERIAL shell kill
 else
     echo "Could not automatically determine OS!"
     exit 1;
 fi
 
 # We need the debug symbols from these files
 GDB_TMP_DIR=$SKIA_OUT/android_gdb_tmp
 mkdir -p $GDB_TMP_DIR
 
 echo "Pushing gdbserver..."
 adb_push_if_needed $ANDROID_TOOLCHAIN/gdbserver /data/local/tmp
 
 # Launch the app
 echo "Launching the app..."
-$ADB $DEVICE_SERIAL shell am start -n com.skia.sample_app/com.skia.SkiaSampleActivity
+$ADB $DEVICE_SERIAL shell "am start -n ${activity} --es cmdLineFlags \"${APP_ARGS[*]:1}\""
 
 # Wait for app process to initialize
 sleep 2
 
 # Attach gdbserver to the app process
-PID=$($ADB shell ps | grep com.skia.sample_app | awk '{print $2}')
+PID=$($ADB shell ps | grep ${activityShort} | awk '{print $2}')
 echo "Attaching to pid: $PID"
 $ADB $DEVICE_SERIAL shell /data/local/tmp/gdbserver :$PORT --attach $PID &
 
 # Wait for gdbserver
 sleep 2
 
 # Set up gdb commands
 GDBSETUP=$GDB_TMP_DIR/gdb.setup
 echo "target remote :$PORT" >> $GDBSETUP
 
 
 # Launch gdb client
 echo "Entering gdb client shell"
 ${ANDROID_TOOLCHAIN}/host_prebuilt/bin/gdb-orig -x $GDBSETUP
 
 # Clean up:
 # We could 'rm -rf $GDB_TMP_DIR', but doing so would cause subsequent debugging
 # sessions to take longer than necessary. The tradeoff is to now force the user
 # to remove the directory when they are done debugging.
 rm $GDBSETUP