Updated error message in PerformanceObserver.observe

third_party/WebKit/Source/core/timing/PerformanceObserver.cpp

Index: third_party/WebKit/Source/core/timing/PerformanceObserver.cpp
diff --git a/third_party/WebKit/Source/core/timing/PerformanceObserver.cpp b/third_party/WebKit/Source/core/timing/PerformanceObserver.cpp
index bbd92920cba7868293214fec83a66ae4715cc663..b1c89825040d17b34a1fce9258bb9972aa9bfa08 100644
--- a/third_party/WebKit/Source/core/timing/PerformanceObserver.cpp
+++ b/third_party/WebKit/Source/core/timing/PerformanceObserver.cpp
@@ -49,7 +49,8 @@ void PerformanceObserver::observe(const PerformanceObserverInit& observerInit,
   }
   if (entryTypes == PerformanceEntry::Invalid) {
     exceptionState.throwTypeError(
-        "A Performance Observer MUST have a non-empty entryTypes attribute.");
+        "A Performance Observer MUST have at least one valid entryType in its "
+        "entryTypes attribute.");
     return;
   }
   m_filterOptions = entryTypes;