First shot at source maps generation in dart2js.

lib/compiler/implementation/dart2js.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('dart2js');
 
 #import('dart:io');
 #import('dart:uri');
 #import('dart:utf');
 
@@ skipping 53 matching lines @@
   }
 }
 
 void compile(List<String> argv) {
   Uri cwd = getCurrentDirectory();
   bool throwOnError = false;
   bool showWarnings = true;
   bool verbose = false;
   Uri libraryRoot = cwd;
   Uri out = cwd.resolve('out.js');
+  Uri sourceMapOut = cwd.resolve('out.js.map');
   Uri packageRoot = null;
   List<String> options = new List<String>();
   bool explicitOut = false;
   bool wantHelp = false;
   bool enableColors = true;
 
   passThrough(String argument) => options.add(argument);
 
   setLibraryRoot(String argument) {
     libraryRoot = cwd.resolve(extractPath(argument));
   }
 
   setPackageRoot(String argument) {
     packageRoot = cwd.resolve(extractPath(argument));
   }
 
   setOutput(String argument) {
     explicitOut = true;
     out = cwd.resolve(nativeToUriPath(extractParameter(argument)));
+    sourceMapOut = new Uri.fromString('$out.map');
   }
 
   handleShortOptions(String argument) {
     var shortOptions = argument.substring(1).splitChars();
     for (var shortOption in shortOptions) {
       switch (shortOption) {
         case 'v':
           verbose = true;
           break;
         case 'h':
@@ skipping 71 matching lines @@
   }
 
   bool isAborting = false;
 
   final int FATAL = api.Diagnostic.CRASH.ordinal | api.Diagnostic.ERROR.ordinal;
   final int INFO =
       api.Diagnostic.INFO.ordinal | api.Diagnostic.VERBOSE_INFO.ordinal;
 
   void handler(Uri uri, int begin, int end, String message,
                api.Diagnostic kind) {
+    if (kind.name === 'source map') {
+      // TODO(podivilov): We should find a better way to return source maps from
+      // emitter. Using diagnostic handler for that purpose is a temporary hack.
+      writeString(sourceMapOut, message);
+      return;
+    }
+
     if (isAborting) return;
     isAborting = kind === api.Diagnostic.CRASH;
     bool fatal = (kind.ordinal & FATAL) != 0;
     bool isInfo = (kind.ordinal & INFO) != 0;
     if (isInfo) {
       assert(uri === null);
       info(message, kind);
       return;
     }
     var color;
@@ skipping 32 matching lines @@
   info('compiling $uri');
   info('package root is $packageRoot');
 
   // TODO(ahe): We expect the future to be complete and call value
   // directly. In effect, we don't support truly asynchronous API.
   String code = api.compile(uri, libraryRoot, packageRoot, provider, handler,
                             options).value;
   if (code === null) {
     fail('Error: Compilation failed.');
   }
+  code = '$code\n//@ sourceMappingURL=${relativize(out, sourceMapOut)}';
   writeString(out, code);
   int jsBytesWritten = code.length;
   info('compiled $dartBytesRead bytes Dart -> $jsBytesWritten bytes JS '
        'in ${relativize(cwd, out)}');
   if (!explicitOut) {
     String input = uriPathToNative(arguments[0]);
     String output = relativize(cwd, out);
     print('Dart file $input compiled to JavaScript: $output');
   }
 }
@@ skipping 118 matching lines @@
     } catch (var ignored) {
       print('Internal error: error while printing exception');
     }
     try {
       print(trace);
     } finally {
       exit(253); // 253 is recognized as a crash by our test scripts.
     }
   }
 }