Enable using SDK summaries in Analysis Server.

pkg/analysis_server/lib/src/server/driver.dart

Index: pkg/analysis_server/lib/src/server/driver.dart
diff --git a/pkg/analysis_server/lib/src/server/driver.dart b/pkg/analysis_server/lib/src/server/driver.dart
index 6228efbd5cdc4e350e265b2c5cab8454c4f08db5..c0537540f2fb0636880a9108959373f2390c23ea 100644
--- a/pkg/analysis_server/lib/src/server/driver.dart
+++ b/pkg/analysis_server/lib/src/server/driver.dart
@@ -399,8 +399,12 @@ class Driver implements ServerStarter {
       // Use DirectoryBasedDartSdk.defaultSdkDirectory, which will make a guess.
       defaultSdkDirectory = DirectoryBasedDartSdk.defaultSdkDirectory;
     }
-    SdkCreator defaultSdkCreator =
-        () => new DirectoryBasedDartSdk(defaultSdkDirectory);
+    SdkCreator defaultSdkCreator = () {
+      DirectoryBasedDartSdk sdk =
+          new DirectoryBasedDartSdk(defaultSdkDirectory);
+      sdk.useSummary = true;
+      return sdk;
+    };
     // TODO(brianwilkerson) It would be nice to avoid creating an SDK that
     // cannot be re-used, but the SDK is needed to create a package map provider
     // in the case where we need to run `pub` in order to get the package map.