Add "mock" compilation feature to dart2js and use it to improve test coverage.

dart/frog/frog_options.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.
 
 /** General options used by the compiler. */
 FrogOptions options;
 
 /** Extracts options from command-line arguments. */
 void parseOptions(String homedir, List<String> args, FileSystem files) {
   assert(options == null);
   options = new FrogOptions(homedir, args, files);
 }
 
 // TODO(sigmund): make into a generic option parser...
 class FrogOptions {
   /** Location of corelib and other special dart libraries. */
   String libDir;
 
   /* The top-level dart script to compile. */
   String dartScript;
 
   /** Where to place the generated code. */
   String outfile;
 
   // TODO(dgrove): fix this. For now, either 'sdk' or 'dev'.
   final config = 'dev';
 
   // Options that modify behavior significantly
   bool legOnly = false;
+  bool allowMockCompilation = false;

[ngeoffray, 2012/03/22 10:04:39]

Good catch :)

   bool enableAsserts = false;
   bool enableTypeChecks = false;
   bool warningsAsErrors = false;
   bool verifyImplements = false; // TODO(jimhug): Implement
   bool compileAll = false;
   bool forceDynamic = false;
   bool dietParse = false;
   bool compileOnly = false;
   bool inferTypes = false;
   bool checkOnly = false;
@@ skipping 68 matching lines @@
 
   bool tryParseSimpleOption(String option) {
     if (!option.startsWith('--')) return false;
     switch (option.replaceAll('_', '-')) {
       case '--leg':
       case '--enable-leg':
       case '--leg-only':
         legOnly = true;
         return true;
 
+      case '--allow-mock-compilation':
+        allowMockCompilation = true;
+        return true;
+
       case '--enable-asserts':
         enableAsserts = true;
         return true;
 
       case '--enable-type-checks':
         enableTypeChecks = true;
         enableAsserts = true;  // TODO(kasperl): Remove once VM stops.
         return true;
 
       case '--verify-implements':
@@ skipping 59 matching lines @@
         enableAsserts = true;
         return true;
 
       case '--unchecked':
         disableBoundsChecks = true;
         return true;
     }
     return false;
   }
 }