Add DirectoryBasedDartSdk.useSummary property.

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

Index: pkg/analyzer/lib/src/generated/sdk_io.dart
diff --git a/pkg/analyzer/lib/src/generated/sdk_io.dart b/pkg/analyzer/lib/src/generated/sdk_io.dart
index 8cdb8f2ee7b430c9063ee734e8642350018ed651..4d21f44fd425d096509fbe2742c130c55a50c2c4 100644
--- a/pkg/analyzer/lib/src/generated/sdk_io.dart
+++ b/pkg/analyzer/lib/src/generated/sdk_io.dart
@@ -207,6 +207,11 @@ class DirectoryBasedDartSdk implements DartSdk {
   JavaFile _libraryDirectory;
 
   /**
+   * The flag that specifies whether SDK summary should be used.
+   */
+  bool _useSummary = false;

[Brian Wilkerson, 2016/02/09 20:41:07]

I don't understand what the value of this flag is or where this code is going
long term. Currently this field is initialized to `false` and explicitly set to
`false` in one place, so it can never be `true`. Will the default change? Will
other clients set it to `true`?

+
+  /**
    * The revision number of this SDK, or `"0"` if the revision number cannot be
    * discovered.
    */
@@ -259,10 +264,12 @@ class DirectoryBasedDartSdk implements DartSdk {
       SourceFactory factory = new SourceFactory([new DartUriResolver(this)]);
       _analysisContext.sourceFactory = factory;
       // Try to use summaries.
-      SdkBundle sdkBundle = _getSummarySdkBundle();
-      if (sdkBundle != null) {
-        _analysisContext.resultProvider =
-            new SdkSummaryResultProvider(_analysisContext, sdkBundle);
+      if (_useSummary) {
+        SdkBundle sdkBundle = _getSummarySdkBundle();
+        if (sdkBundle != null) {
+          _analysisContext.resultProvider =
+              new SdkSummaryResultProvider(_analysisContext, sdkBundle);
+        }
       }
     }
     return _analysisContext;
@@ -390,6 +397,17 @@ class DirectoryBasedDartSdk implements DartSdk {
   List<String> get uris => _libraryMap.uris;
 
   /**
+   * Specify whether SDK summary should be used.  This property can only be set
+   * before [context] was invoked.

[Paul Berry, 2016/02/09 20:36:08]

s/was/is/

+   */
+  void set useSummary(bool use) {
+    if (_analysisContext != null) {
+      throw new StateError('SDK analysis context has been already created.');
+    }
+    _useSummary = use;
+  }
+
+  /**
    * Return the name of the file containing the VM executable.
    */
   String get vmBinaryName {