Make Script::GetTokenLocation() and Script::TokenRangeAtLine() use token streams where possible.

runtime/vm/scanner.h

Index: runtime/vm/scanner.h
diff --git a/runtime/vm/scanner.h b/runtime/vm/scanner.h
index 5d59dee190cc7da32621cba5ecc1976f5fbed032..6cecdd18dd162c9aa29db92bef28de2f6e191cd4 100644
--- a/runtime/vm/scanner.h
+++ b/runtime/vm/scanner.h
@@ -64,15 +64,6 @@ class Scanner : ValueObject {
   // Use CurrentPosition() to extract position.
   void ScanTo(intptr_t token_index);
 
-  // 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();