Add use counters for how often we encounter html comments in scripts

R=yangguo@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1641673002

Cr-Commit-Position: refs/heads/master@{#33561}

include/v8.h

@@ -5457,6 +5457,8 @@ class V8_EXPORT Isolate {
     kPromiseChain = 17,
     kPromiseAccept = 18,
     kPromiseDefer = 19,
+    kHtmlCommentInExternalScript = 20,
+    kHtmlComment = 21,
     kUseCounterFeatureCount  // This enum value must be last.
   };
 

src/parsing/parser.cc

@@ -5148,6 +5148,12 @@ void Parser::Internalize(Isolate* isolate, Handle<Script> script, bool error) {
       isolate->CountUsage(v8::Isolate::UseCounterFeature(feature));
     }
   }
+  if (scanner_.FoundHtmlComment()) {
+    isolate->CountUsage(v8::Isolate::kHtmlComment);
+    if (script->line_offset() == 0 && script->column_offset() == 0) {
+      isolate->CountUsage(v8::Isolate::kHtmlCommentInExternalScript);
+    }
+  }
   isolate->counters()->total_preparse_skipped()->Increment(
       total_preparse_skipped_);
 }

src/parsing/scanner.cc

@@ -39,7 +39,8 @@ void Utf16CharacterStream::ResetToBookmark() { UNREACHABLE(); }
 Scanner::Scanner(UnicodeCache* unicode_cache)
     : unicode_cache_(unicode_cache),
       bookmark_c0_(kNoBookmark),
-      octal_pos_(Location::invalid()) {
+      octal_pos_(Location::invalid()),
+      found_html_comment_(false) {
   bookmark_current_.literal_chars = &bookmark_current_literal_;
   bookmark_current_.raw_literal_chars = &bookmark_current_raw_literal_;
   bookmark_next_.literal_chars = &bookmark_next_literal_;
@@ -438,7 +439,10 @@ Token::Value Scanner::ScanHtmlComment() {
   Advance();
   if (c0_ == '-') {
     Advance();
-    if (c0_ == '-') return SkipSingleLineComment();
+    if (c0_ == '-') {
+      found_html_comment_ = true;
+      return SkipSingleLineComment();
+    }
     PushBack('-');  // undo Advance()
   }
   PushBack('!');  // undo Advance()

src/parsing/scanner.h

@@ -448,6 +448,8 @@ class Scanner {
 
   bool IdentifierIsFutureStrictReserved(const AstRawString* string) const;
 
+  bool FoundHtmlComment() const { return found_html_comment_; }
+
  private:
   // The current and look-ahead token.
   struct TokenDesc {
@@ -473,6 +475,7 @@ class Scanner {
     current_.literal_chars = NULL;
     current_.raw_literal_chars = NULL;
     next_next_.token = Token::UNINITIALIZED;
+    found_html_comment_ = false;
   }
 
   // Support BookmarkScope functionality.
@@ -752,6 +755,9 @@ class Scanner {
   // Whether there is a multi-line comment that contains a
   // line-terminator after the current token, and before the next.
   bool has_multiline_comment_before_next_;
+
+  // Whether this scanner encountered an HTML comment.
+  bool found_html_comment_;
 };
 
 }  // namespace internal