First version of PerformanceObserver

Source/core/timing/PerformanceObserver.idl

Index: Source/core/timing/PerformanceObserver.idl
diff --git a/public/platform/WebImageGenerator.h b/Source/core/timing/PerformanceObserver.idl
similarity index 83%
copy from public/platform/WebImageGenerator.h
copy to Source/core/timing/PerformanceObserver.idl
index bb17f4d6df96a2dcc73efa069d2c6646a2338ab9..f57d9533a980a22af6c9bb54268e5a8941f5496e 100644
--- a/public/platform/WebImageGenerator.h
+++ b/Source/core/timing/PerformanceObserver.idl
@@ -28,21 +28,11 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef WebImageGenerator_h
-#define WebImageGenerator_h
-
-#include "WebCommon.h"
-
-class SkData;
-class SkImageGenerator;
-
-namespace blink {
-
-class BLINK_EXPORT WebImageGenerator {
-public:
-    static SkImageGenerator* create(SkData*);
+// http://w3c.github.io/performance-timeline/#the-performance-observer-interface
+[
+    RuntimeEnabled=PerformanceObserverSupport,  // Experimental flag
+    GarbageCollected,
+] interface PerformanceObserver {
+    [RaisesException] void observe(PerformanceObserverInit options);
+    void disconnect();
 };
-
-} // namespace blink
-
-#endif