Add support for compiling Dart via the FE in dart2js.

pkg/compiler/lib/src/dart2js.dart

 // Copyright (c) 2013, 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.cmdline;
 
 import 'dart:async' show Future;
 import 'dart:convert' show UTF8, LineSplitter;
 import 'dart:io' show exit, File, FileMode, Platform, stdin, stderr;
 
@@ skipping 113 matching lines @@
   bool allowNativeExtensions = false;
   bool trustTypeAnnotations = false;
   bool checkedMode = false;
   List<String> hints = <String>[];
   bool verbose;
   bool throwOnError;
   int throwOnErrorCount;
   bool showWarnings;
   bool showHints;
   bool enableColors;
-  bool loadFromDill = false;
+  bool useKernel = false;
   // List of provided options that imply that output is expected.
   List<String> optionsImplyCompilation = <String>[];
   bool hasDisallowUnsafeEval = false;
   Map<String, dynamic> environment = new Map<String, dynamic>();
 
   void passThrough(String argument) => options.add(argument);
 
   void ignoreOption(String argument) {}
 
   if (BUILD_ID != null) {
@@ skipping 126 matching lines @@
       for (String category in categories) {
         if (!["Client", "Server"].contains(category)) {
           fail('Unsupported library category "$category", '
               'supported categories are: Client, Server, all');
         }
       }
     }
     passThrough('--categories=${categories.join(",")}');
   }
 
-  void setLoadFromDill(String argument) {
-    loadFromDill = true;
+  void setPreviewDart2(String argument) {
+    useKernel = true;
     passThrough(argument);
   }
 
   void handleThrowOnError(String argument) {
     throwOnError = true;
     String parameter = extractParameter(argument, isOptionalArgument: true);
     if (parameter != null) {
       var count = int.parse(parameter);
       throwOnErrorCount = count;
     }
@@ skipping 34 matching lines @@
     new OptionHandler(Flags.suppressHints, (_) {
       showHints = false;
     }),
     // TODO(sigmund): remove entirely after Dart 1.20
     new OptionHandler(
         '--output-type=dart|--output-type=dart-multi|--output-type=js',
         setOutputType),
     // TODO(efortuna): Remove this once kernel global inference is fully
     // implemented.
     new OptionHandler(Flags.kernelGlobalInference, passThrough),
-    new OptionHandler(Flags.useKernel, passThrough),
-    new OptionHandler(Flags.loadFromDill, setLoadFromDill),
+    new OptionHandler(Flags.useKernelInSsa, passThrough),
+    new OptionHandler(Flags.useKernel, setPreviewDart2),
     new OptionHandler(Flags.noFrequencyBasedMinification, passThrough),
     new OptionHandler(Flags.verbose, setVerbose),
     new OptionHandler(Flags.version, (_) => wantVersion = true),
     new OptionHandler('--library-root=.+', setLibraryRoot),
     new OptionHandler('--out=.+|-o.*', setOutput, multipleArguments: true),
     new OptionHandler(Flags.allowMockCompilation, passThrough),
     new OptionHandler(Flags.fastStartup, passThrough),
     new OptionHandler(Flags.genericMethodSyntax, ignoreOption),
     new OptionHandler(Flags.initializingFormalAccess, ignoreOption),
     new OptionHandler('${Flags.minify}|-m', implyCompilation),
@@ skipping 105 matching lines @@
   }
   if (showHints != null) {
     diagnosticHandler.showHints = showHints;
   }
   if (enableColors != null) {
     diagnosticHandler.enableColors = enableColors;
   }
   for (String hint in hints) {
     diagnosticHandler.info(hint, api.Diagnostic.HINT);
   }
-  if (loadFromDill) {
-    diagnosticHandler.autoReadFileUri = true;
-  }
 
   if (wantHelp || wantVersion) {
     helpAndExit(wantHelp, wantVersion, diagnosticHandler.verbose);
   }
 
   if (hasDisallowUnsafeEval) {
     String precompiledName = relativize(
         currentDirectory,
         RandomAccessFileOutputProvider.computePrecompiledUri(out),
         Platform.isWindows);
@@ skipping 97 matching lines @@
       }
     } else if (explicitOutputArguments.isNotEmpty) {
       String input = uriPathToNative(arguments[0]);
       String output = relativize(currentDirectory, out, Platform.isWindows);
       print('Dart file ($input) compiled to JavaScript: $output');
     }
     return result;
   }
 
   Uri script = currentDirectory.resolve(arguments[0]);
+  if (useKernel && script.path.endsWith('.dill')) {
+    diagnosticHandler.autoReadFileUri = true;
+  }
   CompilerOptions compilerOptions = new CompilerOptions.parse(
       entryPoint: script,
       libraryRoot: libraryRoot,
       packageRoot: packageRoot,
       packageConfig: packageConfig,
       packagesDiscoveryProvider: findPackages,
       resolutionInputs: resolutionInputs,
       resolutionOutput: resolveOnly ? resolutionOutput : null,
       options: options,
       environment: environment);
@@ skipping 518 matching lines @@
   @override
   void add(String event) {
     sb.write(event);
   }
 
   @override
   void close() {
     // Do nothing.
   }
 }