Conditionally enable SDK summaries in server

pkg/analyzer/lib/src/generated/sdk.dart

 // Copyright (c) 2014, 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.src.generated.sdk;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
@@ skipping 106 matching lines @@
     return sdkMap.values.first;
   }
 
   /**
    * Return the Dart SDK that is appropriate for the given analysis [options].
    * If such an SDK has not yet been created, then the [sdkCreator] will be
    * invoked to create it.
    */
   DartSdk getSdkForOptions(AnalysisOptions options) {
     int encoding = options.encodeCrossContextOptions();
-    DartSdk sdk = sdkMap[encoding];
-    if (sdk == null) {
-      sdk = sdkCreator(options);
-      sdkMap[encoding] = sdk;
-    }
-    return sdk;
+    return sdkMap.putIfAbsent(encoding, () => sdkCreator(options));

[Brian Wilkerson, 2016/06/01 04:16:51]

This is just code clean-up. I'm happy to back it out if you like.

[pquitslund, 2016/06/01 04:28:17]

I'm all of keeping it.  Yay for opportunistic clean up!

   }
 }
 
 /**
  * A map from Dart library URI's to the [SdkLibraryImpl] representing that
  * library.
  */
 class LibraryMap {
   /**
    * A table mapping Dart library URI's to the library.
@@ skipping 300 matching lines @@
     _platforms |= DART2JS_PLATFORM;
   }
 
   /**
    * Record that this library can be run on the VM.
    */
   void setVmLibrary() {
     _platforms |= VM_PLATFORM;
   }
 }