Scanner cleanups: use isolates to allocate handles and zone objects

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_
 
 #include "vm/growable_array.h"
 #include "vm/token.h"
 
 namespace dart {
 
 // Forward declarations.
 class Array;
 class Library;
 class RawString;
+class ScanContext;
 class String;
 
 // A call to Scan() scans the source one token at at time.
 // The scanned token is returned by cur_token().
 // GetStream() scans the entire source text and returns a stream of tokens.
 class Scanner : ValueObject {
  public:
   typedef int32_t (*CharAtFunc)(const String& str, intptr_t index);
 
   // SourcePosition describes a text location in user friendly
@@ skipping 49 matching lines @@
   bool IsIdent(const String& str);
 
   // Does the token stream contain a valid literal. This is used to implement
   // the Dart methods int.parse and double.parse.
   static bool IsValidLiteral(const Scanner::GrowableTokenStream& tokens,
                              Token::Kind literal_kind,
                              bool* is_positive,
                              const String** value);
 
  private:
+  friend class ScanContext;
+
   static const int kNumLowercaseChars = 26;
 
-  struct ScanContext {
-    ScanContext* next;
-    char string_delimiter;
-    bool string_is_multiline;
-    int  brace_level;
-  };
-
   struct KeywordTable {
     Token::Kind kind;
     const char* keyword_chars;
     int keyword_len;
     const String* keyword_symbol;
   };
 
   // Rewind scanner position to token 0.
   void Reset();
 
@@ skipping 109 matching lines @@
   Isolate* isolate_;
 
   static KeywordTable keywords_[Token::kNumKeywords];
   static int keywords_char_offset_[kNumLowercaseChars];
 };
 
 
 }  // namespace dart
 
 #endif  // VM_SCANNER_H_