Use dev dart in device_doctor. (#2341)

* Use dev dart in device_doctor.

This is to unblock recipe changes impacting device_doctor builders.

* Use latest instead.

* Print ensure_file.

* Back to dev.
diff --git a/device_doctor/tool/build.sh b/device_doctor/tool/build.sh
index 4099dd5..ae3fdfc 100644
--- a/device_doctor/tool/build.sh
+++ b/device_doctor/tool/build.sh
@@ -18,6 +18,11 @@
 DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd)"
 OS="`uname`"
 
+echo ########### Ensure file ###########
+cat $DIR/ensure_file
+echo ###################################
+
+
 cipd ensure -ensure-file $DIR/ensure_file -root $DIR
 
 pushd $DIR/..
diff --git a/device_doctor/tool/ensure_file b/device_doctor/tool/ensure_file
index a6985f8..8efdd50 100644
--- a/device_doctor/tool/ensure_file
+++ b/device_doctor/tool/ensure_file
@@ -1,3 +1,3 @@
 $ServiceURL https://chrome-infra-packages.appspot.com/
 
-dart/dart-sdk/${os}-${arch} beta
+dart/dart-sdk/${os}-${arch} dev
diff --git a/device_doctor/tool/ensure_file_windows b/device_doctor/tool/ensure_file_windows
index a6985f8..8efdd50 100644
--- a/device_doctor/tool/ensure_file_windows
+++ b/device_doctor/tool/ensure_file_windows
@@ -1,3 +1,3 @@
 $ServiceURL https://chrome-infra-packages.appspot.com/
 
-dart/dart-sdk/${os}-${arch} beta
+dart/dart-sdk/${os}-${arch} dev