Provide WebVR pose data only to the focused frame.

third_party/WebKit/Source/modules/vr/VRDisplay.h

Index: third_party/WebKit/Source/modules/vr/VRDisplay.h
diff --git a/third_party/WebKit/Source/modules/vr/VRDisplay.h b/third_party/WebKit/Source/modules/vr/VRDisplay.h
index 7a3d101e1808cb49a6e3c767d55e8fe5c7298cf5..adc9342b9b6acf763b00c247524f793d95643e8e 100644
--- a/third_party/WebKit/Source/modules/vr/VRDisplay.h
+++ b/third_party/WebKit/Source/modules/vr/VRDisplay.h
@@ -92,6 +92,8 @@ class VRDisplay final : public EventTargetWithInlineData,
   // ScriptWrappable implementation.
   bool hasPendingActivity() const final;
 
+  void focusChanged(bool focused);
+
   DECLARE_VIRTUAL_TRACE();
 
  protected:
@@ -148,7 +150,7 @@ class VRDisplay final : public EventTargetWithInlineData,
   Member<VREyeParameters> m_eyeParametersLeft;
   Member<VREyeParameters> m_eyeParametersRight;
   device::mojom::blink::VRPosePtr m_framePose;
-  int16_t m_frameId;
+  int16_t m_frameId = -1;

[haraken, 2017/02/03 18:46:18]

Not related to this CL, we should not expose a frame ID to Blink...

+dcheng@

[mthiesse, 2017/02/03 20:47:29]

I don't think this is the kind of frame ID you're thinking of.

This frame ID is a hacky mechanism for the browser to know which VR Pose each
frame it received was rendered with. The frame ID is literally drawn into the
webVR canvas (as a pixel in the corner), and read back inside the browser.

Even with a compromised renderer, knowing or manipulating this frameID would do
nothing but cause webVR to render incorrectly, which either a correctly
functioning page, or a compromised renderer, could already do anyways.

   VRLayer m_layer;
   double m_depthNear = 0.01;
   double m_depthFar = 10000.0;