VizMainImpl: Remove some unused code.

Bug: none
Change-Id: I987547cfa1a5007ea3e3844afcc6f7c9d8ad9cd9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1810762
Auto-Submit: Peng Huang <penghuang@chromium.org>
Commit-Queue: Jonathan Backer <backer@chromium.org>
Reviewed-by: Jonathan Backer <backer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697653}

components/viz/service/main/viz_main_impl.h

@@ -44,12 +44,6 @@ class MojoUkmRecorder;
 namespace viz {
 class GpuServiceImpl;
 
-#if defined(OS_ANDROID)
-using CompositorThreadType = base::android::JavaHandlerThread;
-#else
-using CompositorThreadType = base::Thread;
-#endif
-
 class VizMainImpl : public mojom::VizMain {
  public:
   struct LogMessage {