Better breakpoint placement

runtime/vm/scanner.h

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // Scanner class for the Dart language. The scanner reads source text
 // and produces a stream of tokens which is used by the parser.
 //
 
 #ifndef VM_SCANNER_H_
 #define VM_SCANNER_H_
@@ skipping 46 matching lines @@
   Scanner(const String& source, const String& private_key);
   ~Scanner();
 
   // Scans one token at a time.
   void Scan();
 
   // Scans to specified token position.
   // Use CurrentPosition() to extract position.
   void ScanTo(intptr_t token_index);
 
-  // Returns token index of first token on or after given line number.
-  // Returns negative value if no token exists on or after the line.
-  intptr_t TokenIndexAtLine(intptr_t line_number);
+  // Returns index of first and last token on the given line.
+  // Returns both indices < 0 if no token exists on or after the line.
+  // If a token exists after, but not on given line, returns in
+  // *fisrt_token_index the index of the first token after the line,
+  // and a negative value in *last_token_index.
+  void TokenRangeAtLine(intptr_t line_number,
+                        intptr_t* first_token_index,
+                        intptr_t* last_token_index);
 
   // Scans entire source and returns a stream of tokens.
   // Should be called only once.
   const GrowableTokenStream& GetStream();
 
   // Info about most recently recognized token.
   const TokenDescriptor& current_token() const { return current_token_; }
 
   // Was there a line break before the current token?
   bool NewlineBeforeToken() const { return newline_seen_; }
@@ skipping 131 matching lines @@
 
   SourcePosition c0_pos_;      // Source position of lookahead character c0_.
   KeywordTable keywords_[Token::numKeywords];
   Array& keyword_symbol_table_;  // Access to keyword symbols in object store.
 };
 
 
 }  // namespace dart
 
 #endif  // VM_SCANNER_H_