EDK: mostly style fix: change TestIOThread::Mode to an enum class.

mojo/edk/test/test_io_thread.h

Index: mojo/edk/test/test_io_thread.h
diff --git a/mojo/edk/test/test_io_thread.h b/mojo/edk/test/test_io_thread.h
index 78b0b015f9f53fa01c59182a4ba791c7fb2d5507..0b0f5dd2e480e734b521a4a71e0d676ee8e57851 100644
--- a/mojo/edk/test/test_io_thread.h
+++ b/mojo/edk/test/test_io_thread.h
@@ -17,8 +17,8 @@ namespace test {
 // Class to help create/run threads with I/O |MessageLoop|s in tests.
 class TestIOThread {
  public:
-  enum Mode { kAutoStart, kManualStart };
-  explicit TestIOThread(Mode mode);
+  enum class StartMode { AUTO, MANUAL };
+  explicit TestIOThread(StartMode start_mode);
   // Stops the I/O thread if necessary.
   ~TestIOThread();