Add support for watch events and error notifications

pkg/analyzer/lib/context/context_root.dart

Index: pkg/analyzer/lib/context/context_root.dart
diff --git a/pkg/analyzer/lib/context/context_root.dart b/pkg/analyzer/lib/context/context_root.dart
index f871ab1c0a8993bd93aa8895d26917d86bddc601..cfc47ff8f99c2c0ebbadbf3ed75c5cbb49422994 100644
--- a/pkg/analyzer/lib/context/context_root.dart
+++ b/pkg/analyzer/lib/context/context_root.dart
@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer/src/generated/utilities_general.dart';
+import 'package:path/path.dart' as path;
 
 /**
  * Information about the root directory associated with an analysis context.
@@ -45,6 +46,24 @@ class ContextRoot {
   }
 
   /**
+   * Return `true` if the file with the given [filePath] is contained within
+   * this context root. A file contained in a context root if it is within the
+   * context [root] neither explicitly excluded or within one of the excluded
+   * directories.
+   */
+  bool containsFile(String filePath) {
+    if (!path.isWithin(root, filePath)) {
+      return false;
+    }
+    for (String excluded in exclude) {
+      if (filePath == excluded || path.isWithin(excluded, filePath)) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  /**
    * Compare the lists [listA] and [listB], using [itemEqual] to compare
    * list elements.
    */