Only count legacy parser usage if legacy parser had effect.

We would otherwise also count if its just trimming whitespaces.

R=adamk@chromium.org
BUG=chromium:618595

Review-Url: https://codereview.chromium.org/2080183003
Cr-Commit-Position: refs/heads/master@{#37197}

src/dateparser-inl.h

@@ -75,11 +75,12 @@ bool DateParser::Parse(Isolate* isolate, Vector<Char> str, FixedArray* out) {
   if (next_unhandled_token.IsInvalid()) return false;
   bool has_read_number = !day.IsEmpty();
   // If there's anything left, continue with the legacy parser.
-  bool legacy_parser = !next_unhandled_token.IsEndOfInput();
+  bool legacy_parser = false;
   for (DateToken token = next_unhandled_token;
        !token.IsEndOfInput();
        token = scanner.Next()) {
     if (token.IsNumber()) {
+      legacy_parser = true;
       has_read_number = true;
       int n = token.number();
       if (scanner.SkipSymbol(':')) {
@@ -115,6 +116,7 @@ bool DateParser::Parse(Isolate* isolate, Vector<Char> str, FixedArray* out) {
         scanner.SkipSymbol('-');
       }
     } else if (token.IsKeyword()) {
+      legacy_parser = true;
       // Parse a "word" (sequence of chars. >= 'A').
       KeywordType type = token.keyword_type();
       int value = token.keyword_value();
@@ -133,6 +135,7 @@ bool DateParser::Parse(Isolate* isolate, Vector<Char> str, FixedArray* out) {
         if (scanner.Peek().IsNumber()) return false;
       }
     } else if (token.IsAsciiSign() && (tz.IsUTC() || !time.IsEmpty())) {
+      legacy_parser = true;
       // Parse UTC offset (only after UTC or time).
       tz.SetSign(token.ascii_sign());
       // The following number may be empty.

test/cctest/test-date.cc

@@ -167,6 +167,32 @@ TEST(DaylightSavingsTime) {
   CheckDST(august_20);
 }
 
+namespace {
+int legacy_parse_count = 0;
+void DateParseLegacyCounterCallback(v8::Isolate* isolate,
+                                    v8::Isolate::UseCounterFeature feature) {
+  if (feature == v8::Isolate::kLegacyDateParser) legacy_parse_count++;
+}
+}  // anonymous namespace
+
+TEST(DateParseLegacyUseCounter) {
+  CcTest::InitializeVM();
+  v8::HandleScope scope(CcTest::isolate());
+  LocalContext context;
+  CcTest::isolate()->SetUseCounterCallback(DateParseLegacyCounterCallback);
+  CHECK_EQ(0, legacy_parse_count);
+  CompileRun("Date.parse('2015-02-31')");
+  CHECK_EQ(0, legacy_parse_count);
+  CompileRun("Date.parse('2015-02-31T11:22:33.444Z01:23')");
+  CHECK_EQ(0, legacy_parse_count);
+  CompileRun("Date.parse('2015-02-31T11:22:33.444')");
+  CHECK_EQ(0, legacy_parse_count);
+  CompileRun("Date.parse('2000 01 01')");
+  CHECK_EQ(1, legacy_parse_count);
+  CompileRun("Date.parse('2015-02-31T11:22:33.444     ')");
+  CHECK_EQ(1, legacy_parse_count);
+}
+
 #ifdef V8_I18N_SUPPORT
 TEST(DateCacheVersion) {
   FLAG_allow_natives_syntax = true;