Turn ThreadPriority enum into an enum class.

content/renderer/gpu/compositor_output_surface.cc

Index: content/renderer/gpu/compositor_output_surface.cc
diff --git a/content/renderer/gpu/compositor_output_surface.cc b/content/renderer/gpu/compositor_output_surface.cc
index 0ce2973d05ca2052ef4f9ca01dd5a15837e20ca3..bdeefe0a8fc98208ccd3b0deea0e018a61cb0c64 100644
--- a/content/renderer/gpu/compositor_output_surface.cc
+++ b/content/renderer/gpu/compositor_output_surface.cc
@@ -215,12 +215,12 @@ bool CompositorOutputSurface::Send(IPC::Message* message) {
 namespace {
 #if defined(OS_ANDROID)
   void SetThreadPriorityToIdle(base::PlatformThreadHandle handle) {
-    base::PlatformThread::SetThreadPriority(
-       handle, base::kThreadPriority_Background);
+    base::PlatformThread::SetThreadPriority(handle,
+                                            base::ThreadPriority::BACKGROUND);
   }
   void SetThreadPriorityToDefault(base::PlatformThreadHandle handle) {
-    base::PlatformThread::SetThreadPriority(
-       handle, base::kThreadPriority_Normal);
+    base::PlatformThread::SetThreadPriority(handle,
+                                            base::ThreadPriority::NORMAL);
   }
 #else
   void SetThreadPriorityToIdle(base::PlatformThreadHandle handle) {}