Enable developer options for TraceurUiTests

We recently changed Traceur to automatically close if development
options are disabled. This change invokes a tradefed preparer to enable
developer options at test setup, and to restore the previous setting
after.

Bug: 109751037
Test: TraceurUiTests
Change-Id: I3035bdfa5f5c37550aef4015fab3a081646698e8
1 file changed