Add support for --no-colors to make it easier to integrate dart2js in the editor.

lib/compiler/implementation/source_file.dart

 // Copyright (c) 2012, 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('source_file');
 
-#import('colors.dart');
+#import('colors.dart', prefix: 'colors');
 
 /**
  * Represents a file of source code.
  */
 class SourceFile {
 
   /** The name of the file. */
   final String filename;
 
   /** The text content of the file. */
@@ skipping 29 matching lines @@
 
   int getColumn(int line, int position) {
     return position - lineStarts[line];
   }
 
   /**
    * Create a pretty string representation from a character position
    * in the file.
    */
   String getLocationMessage(String message, int start,
-      [int end, bool includeText=false, bool useColors = true]) {
+      [int end, bool includeText = false]) {
     var line = getLine(start);
     var column = getColumn(line, start);
 
     var buf = new StringBuffer(
         '${filename}:${line + 1}:${column + 1}: $message');
     if (includeText) {
       buf.add('\n');
       var textLine;
       // +1 for 0-indexing, +1 again to avoid the last line of the file
       if ((line + 2) < _lineStarts.length) {
         textLine = text.substring(_lineStarts[line], _lineStarts[line+1]);
       } else {
         textLine = text.substring(_lineStarts[line]) + '\n';
       }
 
       int toColumn = Math.min(column + (end-start), textLine.length);
-      if (useColors) {
+      if (colors.enabled) {
         buf.add(textLine.substring(0, column));
-        buf.add(RED_COLOR);
+        buf.add(colors.RED_COLOR);
         buf.add(textLine.substring(column, toColumn));
-        buf.add(NO_COLOR);
+        buf.add(colors.NO_COLOR);
         buf.add(textLine.substring(toColumn));
       } else {
         buf.add(textLine);
       }
 
       int i = 0;
       for (; i < column; i++) {
         buf.add(' ');
       }
 
-      if (useColors) buf.add(RED_COLOR);
+      if (colors.enabled) buf.add(colors.RED_COLOR);
       for (; i < toColumn; i++) {
         buf.add('^');
       }
-      if (useColors) buf.add(NO_COLOR);
+      if (colors.enabled) buf.add(colors.NO_COLOR);
     }
 
     return buf.toString();
   }
 }