[vr] Add a frame rate counter for the vr UI

chrome/browser/android/vr_shell/vr_shell_gl.h

Index: chrome/browser/android/vr_shell/vr_shell_gl.h
diff --git a/chrome/browser/android/vr_shell/vr_shell_gl.h b/chrome/browser/android/vr_shell/vr_shell_gl.h
index 68d7a5cd4683ade63a5360d45440f80da8d8e8c1..519baa85dd7b6cca3431740d1a005cef8b112f97 100644
--- a/chrome/browser/android/vr_shell/vr_shell_gl.h
+++ b/chrome/browser/android/vr_shell/vr_shell_gl.h
@@ -30,6 +30,10 @@ namespace blink {
 class WebInputEvent;
 }
 
+namespace cc {
+class FrameRateCounter;
+}
+
 namespace gl {
 class GLContext;
 class GLSurface;
@@ -239,6 +243,8 @@ class VrShellGl : public device::mojom::VRVSyncProvider {
   // Attributes for gesture detection while holding app button.
   gvr::Vec3f controller_start_direction_;
 
+  std::unique_ptr<cc::FrameRateCounter> frame_rate_counter_;
+
   base::WeakPtrFactory<VrShellGl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(VrShellGl);