Remove dependency on dart:json.

dart/lib/compiler/implementation/util/util.dart

 // 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.
 
 library org_dartlang_compiler_util;
 
 import 'util_implementation.dart';
+import 'characters.dart';
 
 part 'link.dart';
 
 /**
  * Tagging interface for classes from which source spans can be generated.
  */
 // TODO(johnniwinther): Find a better name.
 // TODO(ahe): How about "Bolt"?
 abstract class Spannable {}
 
 class SpannableAssertionFailure {
   final Spannable node;
   final String message;
   SpannableAssertionFailure(this.node, this.message);
 
   String toString() => 'compiler crashed.';
 }
+
+/// Writes the characters of [iterator] on [buffer].  The characters
+/// are escaped as suitable for JavaScript and JSON.  [buffer] is
+/// anything which supports [:add:] and [:addCharCode:], for example,
+/// [StringBuffer].
+void writeJsonEscapedCharsOn(Iterator<int> iterator, buffer, onError(code)) {
+  while (iterator.hasNext) {
+    int code = iterator.next();
+    if (identical(code, $SQ)) {
+      buffer.add(r"\'");
+    } else if (identical(code, $LF)) {
+      buffer.add(r'\n');
+    } else if (identical(code, $CR)) {
+      buffer.add(r'\r');
+    } else if (identical(code, $LS)) {
+      // This Unicode line terminator and $PS are invalid in JS string
+      // literals.
+      buffer.add(r'\u2028');
+    } else if (identical(code, $PS)) {
+      buffer.add(r'\u2029');
+    } else if (identical(code, $BACKSLASH)) {
+      buffer.add(r'\\');
+    } else {
+      if (code > 0xffff) {
+        if (onError != null) onError(code);
+        throw 'Unhandled non-BMP character: ${code.toRadixString(16)}';
+      }
+      // TODO(lrn): Consider whether all codes above 0x7f really need to
+      // be escaped. We build a Dart string here, so it should be a literal
+      // stage that converts it to, e.g., UTF-8 for a JS interpreter.
+      if (code < 0x20) {
+        buffer.add(r'\x');
+        if (code < 0x10) buffer.add('0');
+        buffer.add(code.toRadixString(16));
+      } else if (code >= 0x80) {
+        if (code < 0x100) {
+          buffer.add(r'\x');
+        } else {
+          buffer.add(r'\u');
+          if (code < 0x1000) {
+            buffer.add('0');
+          }
+        }
+        buffer.add(code.toRadixString(16));
+      } else {
+        buffer.addCharCode(code);
+      }
+    }
+  }
+}