add --sync to adb push in bin/droid

This skips pushing files that are already present.

Change-Id: Ibe86be1e553da3cbe9d02d00764164d9e0745f8d
Reviewed-on: https://skia-review.googlesource.com/138164
Commit-Queue: Mike Klein <mtklein@chromium.org>
Commit-Queue: Hal Canary <halcanary@google.com>
Auto-Submit: Mike Klein <mtklein@chromium.org>
Reviewed-by: Hal Canary <halcanary@google.com>
diff --git a/bin/droid b/bin/droid
index c633181..cb48e36 100755
--- a/bin/droid
+++ b/bin/droid
@@ -16,7 +16,7 @@
 set -e
 set -x
 
-adb push $path //data/local/tmp/
-adb push resources //data/local/tmp/
+adb push --sync $path //data/local/tmp/
+adb push --sync resources //data/local/tmp/
 adb shell "chmod +x //data/local/tmp/$name"
 adb shell "cd //data/local/tmp; ./$name $args"