Fix 'debugging on Android' android_gdb_app script.

1) com.skia -> com.skia.sample_app
2) pass arguments to android_gdb_app to android_setup.sh so you can build gdbserver binaries for your actual device(rather than default arm64). This allows you to run it like this for example:

  ./platform_tools/android/bin/android_gdb_app -d nexus_6

BUG=skia:
DOCS_PREVIEW= https://skia.org/?cl=1509853006

Review URL: https://codereview.chromium.org/1509853006
diff --git a/platform_tools/android/bin/android_gdb_app b/platform_tools/android/bin/android_gdb_app
index 31cf991..f0879fa 100755
--- a/platform_tools/android/bin/android_gdb_app
+++ b/platform_tools/android/bin/android_gdb_app
@@ -4,7 +4,7 @@
 # the debugging environment.
 
 SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-source $SCRIPT_DIR/android_setup.sh
+source $SCRIPT_DIR/android_setup.sh "$@"
 
 APP_NAME=${APP_ARGS[0]}
 PORT=5039
@@ -31,21 +31,21 @@
 echo "Copying symbol files"
 adb_pull_if_needed /system/bin/app_process $GDB_TMP_DIR
 adb_pull_if_needed /system/lib/libc.so $GDB_TMP_DIR
-adb_pull_if_needed /data/data/com.skia/lib/libskia_android.so $GDB_TMP_DIR
-adb_pull_if_needed /data/data/com.skia/lib/libSampleApp.so $GDB_TMP_DIR
+adb_pull_if_needed /data/data/com.skia.sample_app/lib/libskia_android.so $GDB_TMP_DIR
+adb_pull_if_needed /data/data/com.skia.sample_app/lib/libSampleApp.so $GDB_TMP_DIR
 
 echo "Pushing gdbserver..."
 adb_push_if_needed $ANDROID_TOOLCHAIN/../gdbserver /data/local/tmp
 
 # Launch the app
 echo "Launching the app..."
-$ADB $DEVICE_SERIAL shell am start -n com.skia/com.skia.SkiaSampleActivity
+$ADB $DEVICE_SERIAL shell am start -n com.skia.sample_app/com.skia.SkiaSampleActivity
 
 # Wait for app process to initialize
 sleep 2
 
 # Attach gdbserver to the app process
-PID=$($ADB shell ps | grep com.skia | awk '{print $2}')
+PID=$($ADB shell ps | grep com.skia.sample_app | awk '{print $2}')
 echo "Attaching to pid: $PID"
 $ADB $DEVICE_SERIAL shell /data/local/tmp/gdbserver :$PORT --attach $PID &
 
diff --git a/site/user/quick/android.md b/site/user/quick/android.md
index e689d6f..bffde08 100644
--- a/site/user/quick/android.md
+++ b/site/user/quick/android.md
@@ -201,7 +201,7 @@
     
     # SAMPLE APP
     # make sure you've installed the app on the device first
-    ./platform_tools/android/bin/android_gdb_app
+    ./platform_tools/android/bin/android_gdb_app [-d device_id]
 
 When the gdb client is ready, insert a breakpoint, and continue to let the
 program resume execution.