dart2js: add support for configuration-specific imports.

pkg/compiler/lib/src/compiler.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.compiler_base;
 
 import 'dart:async' show
     EventSink,
     Future;
 
@@ skipping 502 matching lines @@
             this.useFrequencyNamer: false,
             this.verbose: false,
             this.sourceMapUri: null,
             this.outputUri: null,
             this.buildId: UNDETERMINED_BUILD_ID,
             this.terseDiagnostics: false,
             this.deferredMapUri: null,
             this.dumpInfo: false,
             this.showPackageWarnings: false,
             bool useStartupEmitter: false,
+            bool enableConditionalDirectives: false,
             this.useContentSecurityPolicy: false,
             this.suppressWarnings: false,
             this.fatalWarnings: false,
             bool hasIncrementalSupport: false,
             this.enableExperimentalMirrors: false,
             this.enableAssertMessage: false,
             this.allowNativeExtensions: false,
             this.generateCodeWithCompileTimeErrors: false,
             this.testMode: false,
             api.CompilerOutput outputProvider,
@@ skipping 42 matching lines @@
                                              multiFile: dart2dartMultiFile);
       if (dumpInfo) {
         throw new ArgumentError('--dump-info is not supported for dart2dart.');
       }
     }
 
     tasks = [
       libraryLoader = new LibraryLoaderTask(this),
       serialization = new SerializationTask(this),
       scanner = new ScannerTask(this),
-      dietParser = new DietParserTask(this),
-      parser = new ParserTask(this),
-      patchParser = new PatchParserTask(this),
+      dietParser = new DietParserTask(
+          this, enableConditionalDirectives: enableConditionalDirectives),
+      parser = new ParserTask(
+          this, enableConditionalDirectives: enableConditionalDirectives),
+      patchParser = new PatchParserTask(
+          this, enableConditionalDirectives: enableConditionalDirectives),
       resolver = new ResolverTask(this, backend.constantCompilerTask),
       closureToClassMapper = new closureMapping.ClosureTask(this),
       checker = new TypeCheckerTask(this),
       typesTask = new ti.TypesTask(this),
       constants = backend.constantCompilerTask,
       deferredLoadTask = new DeferredLoadTask(this),
       mirrorUsageAnalyzerTask = new MirrorUsageAnalyzerTask(this),
       enqueuer = new EnqueueTask(this),
       dumpInfoTask = new DumpInfoTask(this),
       reuseLibraryTask = new GenericTask('Reuse library', this),
@@ skipping 1332 matching lines @@
 
   @override
   void parsePatchClass(ClassElement cls) {
     compiler.patchParser.measure(() {
       if (cls.isPatch) {
         compiler.patchParser.parsePatchClassNode(cls);
       }
     });
   }
 }