Add UseCounter for Date.parse's legacy parse heuristics.

third_party/WebKit/Source/bindings/core/v8/V8PerIsolateData.cpp

Index: third_party/WebKit/Source/bindings/core/v8/V8PerIsolateData.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/V8PerIsolateData.cpp b/third_party/WebKit/Source/bindings/core/v8/V8PerIsolateData.cpp
index e30d25eab49fae51ab25592e76ccea254e8146aa..9596c370b265ae516953d1eecae6f841aaa6ca54 100644
--- a/third_party/WebKit/Source/bindings/core/v8/V8PerIsolateData.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/V8PerIsolateData.cpp
@@ -191,6 +191,9 @@ void V8PerIsolateData::useCounterCallback(v8::Isolate* isolate, v8::Isolate::Use
     case v8::Isolate::kDecimalWithLeadingZeroInStrictMode:
         blinkFeature = UseCounter::V8DecimalWithLeadingZeroInStrictMode;
         break;
+    case v8::Isolate::kLegacyDateParser:
+        blinkFeature = UseCounter::V8LegacyDateParser;
+        break;
     default:
         // This can happen if V8 has added counters that this version of Blink
         // does not know about. It's harmless.