Implement AnalysisDriver.getSourceKind() and use it in analyzer-cli.

pkg/analyzer_cli/lib/src/driver.dart

 // Copyright (c) 2015, 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 analyzer_cli.src.driver;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io' as io;
 
@@ skipping 212 matching lines @@
       } else {
         context.applyChanges(changeSet);
       }
     }
 
     // Analyze the libraries.
     ErrorSeverity allResult = ErrorSeverity.NONE;
     var libUris = <Uri>[];
     var parts = <Source>[];
     for (Source source in sourcesToAnalyze) {
-      if (context.computeKindOf(source) == SourceKind.PART) {
+      SourceKind sourceKind = analysisDriver != null
+          ? await analysisDriver.getSourceKind(source.fullName)
+          : context.computeKindOf(source);
+      if (sourceKind == SourceKind.PART) {
         parts.add(source);
         continue;
       }
       ErrorSeverity status = await _runAnalyzer(source, options);
       allResult = allResult.max(status);
       libUris.add(source.uri);
     }
 
     // Check that each part has a corresponding source in the input list.
     for (Source part in parts) {
@@ skipping 669 matching lines @@
     for (var package in packages) {
       var packageName = path.basename(package.path);
       var realPath = package.resolveSymbolicLinksSync();
       result[packageName] = [
         PhysicalResourceProvider.INSTANCE.getFolder(realPath)
       ];
     }
     return result;
   }
 }