Presentation API: add UMA.

Source/modules/presentation/PresentationRequest.idl

Index: Source/modules/presentation/PresentationRequest.idl
diff --git a/Source/modules/presentation/PresentationRequest.idl b/Source/modules/presentation/PresentationRequest.idl
index ce65c73724b3baa8650a650422b66312154d69bf..9c4aec87f3b146e9e596d54558bef8dc32608779 100644
--- a/Source/modules/presentation/PresentationRequest.idl
+++ b/Source/modules/presentation/PresentationRequest.idl
@@ -11,10 +11,11 @@
     RaisesException=Constructor,
     GarbageCollected,
     RuntimeEnabled=Presentation,
+    MeasureAs=PresentationRequestConstructor
 ] interface PresentationRequest : EventTarget {
-    [CallWith=ScriptState] Promise<PresentationSession> start();
-    [CallWith=ScriptState] Promise<PresentationSession> join(DOMString id);
-    [CallWith=ScriptState] Promise<PresentationAvailability> getAvailability();
+    [CallWith=ScriptState, MeasureAs=PresentationRequestStart] Promise<PresentationSession> start();
+    [CallWith=ScriptState, MeasureAs=PresentationRequestJoin] Promise<PresentationSession> join(DOMString id);
+    [CallWith=ScriptState, MeasureAs=PresentationRequestGetAvailability] Promise<PresentationAvailability> getAvailability();
 
     attribute EventHandler onsessionconnect;
 };