Ensure display metrics on display service creation

This fixes a potential race condition where a VR app could request the
display metrics from the VR display service before it actually queries
them from the HWC.

Bug: None
Test: Compiled and ran Vr app.
Change-Id: Ie95b7f5a8ef2e286c7b2994ca94fd87214567e24
diff --git a/libs/vr/libvrflinger/hardware_composer.h b/libs/vr/libvrflinger/hardware_composer.h
index b6aa807..e2a8b90 100644
--- a/libs/vr/libvrflinger/hardware_composer.h
+++ b/libs/vr/libvrflinger/hardware_composer.h
@@ -189,6 +189,10 @@
   HardwareComposer(Hwc2::Composer* hidl);
   ~HardwareComposer();
 
+  bool Initialize();
+
+  bool IsInitialized() const { return initialized_; }
+
   bool Suspend();
   bool Resume();
 
@@ -303,6 +307,8 @@
 
   void HandlePendingScreenshots();
 
+  bool initialized_;
+
   // Hardware composer HAL device.
   std::unique_ptr<Hwc2::Composer> hwc2_hidl_;
   sp<ComposerCallback> callbacks_;