Add UseCounters to measure usage of WebXR

TBR=vollick@chromium.org
BUG=824825

Change-Id: I22bb8ca8287ba4d774d56fe48c66f5d0fd25418d
Reviewed-on: https://chromium-review.googlesource.com/1003139
Commit-Queue: Klaus Weidner <klausw@chromium.org>
Reviewed-by: Klaus Weidner <klausw@chromium.org>
Reviewed-by: David Dorwin <ddorwin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550101}

third_party/blink/public/platform/web_feature.mojom

@@ -1902,6 +1902,11 @@ enum WebFeature {
   kCrossOriginHTMLFrameElementContentDocument = 2410,
   kCrossOriginHTMLObjectElementContentDocument = 2411,
   kCrossOriginHTMLObjectElementGetSVGDocument = 2412,
+  kNavigatorXR = 2413,
+  kXRRequestDevice = 2414,
+  kXRRequestSession = 2415,
+  kXRSupportsSession = 2416,
+  kXRSessionGetInputSources = 2417,
 
   // Add new features immediately above this line. Don't change assigned
   // numbers of any item, and don't reuse removed slots.

third_party/blink/renderer/modules/vr/navigator_vr.idl

@@ -7,7 +7,7 @@
     ImplementedAs=NavigatorVR
 ] partial interface Navigator {
     // Latest API
-    [SecureContext, OriginTrialEnabled=WebXR] readonly attribute XR xr;
+    [SecureContext, OriginTrialEnabled=WebXR, MeasureAs=NavigatorXR] readonly attribute XR xr;
 
     // Legacy API
     [OriginTrialEnabled=WebVR, CallWith=ScriptState] Promise getVRDisplays();

third_party/blink/renderer/modules/xr/xr.idl

@@ -8,5 +8,5 @@
     OriginTrialEnabled=WebXR
 ] interface XR : EventTarget {
   attribute EventHandler ondevicechange;
-  [CallWith=ScriptState] Promise requestDevice();
+  [CallWith=ScriptState, MeasureAs=XRRequestDevice] Promise requestDevice();
 };

third_party/blink/renderer/modules/xr/xr_device.idl

@@ -7,6 +7,6 @@
     SecureContext,
     OriginTrialEnabled=WebXR
 ] interface XRDevice : EventTarget {
-  [CallWith=ScriptState] Promise supportsSession([PermissiveDictionaryConversion] optional XRSessionCreationOptions options);
-  [CallWith=ScriptState] Promise requestSession([PermissiveDictionaryConversion] optional XRSessionCreationOptions options);
+  [CallWith=ScriptState, MeasureAs=XRSupportsSession] Promise supportsSession([PermissiveDictionaryConversion] optional XRSessionCreationOptions options);
+  [CallWith=ScriptState, MeasureAs=XRRequestSession] Promise requestSession([PermissiveDictionaryConversion] optional XRSessionCreationOptions options);
 };

third_party/blink/renderer/modules/xr/xr_session.idl

@@ -26,7 +26,7 @@
   long requestAnimationFrame(XRFrameRequestCallback callback);
   void cancelAnimationFrame(long handle);
 
-  FrozenArray<XRInputSource> getInputSources();
+  [MeasureAs=XRSessionGetInputSources] FrozenArray<XRInputSource> getInputSources();
 
   [CallWith=ScriptState] Promise<void> end();
 };

tools/metrics/histograms/enums.xml

@@ -18265,6 +18265,11 @@ Called by update_net_error_codes.py.-->
   <int value="2410" label="CrossOriginHTMLFrameElementContentDocument"/>
   <int value="2411" label="CrossOriginHTMLObjectElementContentDocument"/>
   <int value="2412" label="CrossOriginHTMLObjectElementGetSVGDocument"/>
+  <int value="2413" label="NavigatorXR"/>
+  <int value="2414" label="XRRequestDevice"/>
+  <int value="2415" label="XRRequestSession"/>
+  <int value="2416" label="XRSupportsSession"/>
+  <int value="2417" label="XRSessionGetInputSources"/>
 </enum>
 
 <enum name="FeedbackSource">