chromeos: Roll system_api dep to 70e37fee.

This picks up new power manager constants for
screen-brightness-related method calls.

BUG=119743,chromium-os:26935
TEST=manual: it builds

Review URL: https://chromiumcodereview.appspot.com/9854007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@128845 0039d316-1c4b-4281-b951-d872f2087c98

tools/cros.DEPS/DEPS

@@ -7,6 +7,6 @@ deps_os = {
     "src/third_party/cros":
       Var("chromiumos_git") + "/platform/cros.git@377f51d8",
     "src/third_party/cros_system_api":
-      Var("chromiumos_git") + "/platform/system_api.git@8da6bc42",
+      Var("chromiumos_git") + "/platform/system_api.git@70e37fee",
   }
 }