Fix PerformanceObserver.supportedEntryTypes externs definition.
@@ -372,7 +372,7 @@ PerformanceObserver.prototype.disconnect = function() {};
PerformanceObserver.prototype.takeRecords = function() {};
/** @const {!Array<string>} */
-PerformanceObserver.prototype.supportedEntryTypes;
+PerformanceObserver.supportedEntryTypes;
/**
* @record
