Add use counters for lots of DOM APIs.

third_party/WebKit/Source/modules/eventsource/EventSource.idl

Index: third_party/WebKit/Source/modules/eventsource/EventSource.idl
diff --git a/third_party/WebKit/Source/modules/eventsource/EventSource.idl b/third_party/WebKit/Source/modules/eventsource/EventSource.idl
index fc77eaa6d66d5c21d2c5935406262a90bb15a9cb..e0f4d4be538c8b77d42c6e9445e2bcb7a038593a 100644
--- a/third_party/WebKit/Source/modules/eventsource/EventSource.idl
+++ b/third_party/WebKit/Source/modules/eventsource/EventSource.idl
@@ -39,18 +39,18 @@
     Exposed=(Window,Worker),
     RaisesException=Constructor,
 ] interface EventSource : EventTarget {
-    readonly attribute DOMString url;
-    readonly attribute boolean withCredentials;
+    [MeasureAs=EventSourceAPI] readonly attribute DOMString url;
+    [MeasureAs=EventSourceAPI] readonly attribute boolean withCredentials;
 
     // ready state
     const unsigned short CONNECTING = 0;
     const unsigned short OPEN = 1;
     const unsigned short CLOSED = 2;
-    readonly attribute unsigned short readyState;
+    [MeasureAs=EventSourceAPI] readonly attribute unsigned short readyState;
 
     // networking
-    attribute EventHandler onopen;
-    attribute EventHandler onmessage;
-    attribute EventHandler onerror;
-    void close();
+    [MeasureAs=EventSourceAPI] attribute EventHandler onopen;
+    [MeasureAs=EventSourceAPI] attribute EventHandler onmessage;
+    [MeasureAs=EventSourceAPI] attribute EventHandler onerror;
+    [MeasureAs=EventSourceAPI] void close();
 };