Add context information to driver and add hooks for plugin management

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
new file mode 100644
index 0000000000000000000000000000000000000000..f871ab1c0a8993bd93aa8895d26917d86bddc601
--- /dev/null
+++ b/pkg/analyzer/lib/context/context_root.dart
@@ -0,0 +1,68 @@
+// Copyright (c) 2017, 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.
+
+import 'package:analyzer/src/generated/utilities_general.dart';
+
+/**
+ * Information about the root directory associated with an analysis context.
+ *
+ * Clients may not extend, implement or mix-in this class.
+ */
+class ContextRoot {
+  /**
+   * The absolute path of the root directory containing the files to be
+   * analyzed.
+   */
+  final String root;
+
+  /**
+   * A list of the absolute paths of files and directories within the root
+   * directory that should not be analyzed.
+   */
+  final List<String> exclude;
+
+  /**
+   * Initialize a newly created context root.
+   */
+  ContextRoot(this.root, this.exclude);
+
+  @override
+  int get hashCode {
+    int hash = 0;
+    hash = JenkinsSmiHash.combine(hash, root.hashCode);
+    hash = JenkinsSmiHash.combine(hash, exclude.hashCode);
+    return JenkinsSmiHash.finish(hash);
+  }
+
+  @override
+  bool operator ==(other) {
+    if (other is ContextRoot) {
+      return root == other.root &&
+          _listEqual(exclude, other.exclude, (String a, String b) => a == b);
+    }
+    return false;
+  }
+
+  /**
+   * Compare the lists [listA] and [listB], using [itemEqual] to compare
+   * list elements.
+   */
+  bool _listEqual(List listA, List listB, bool itemEqual(a, b)) {
+    if (listA == null) {
+      return listB == null;
+    }
+    if (listB == null) {
+      return false;
+    }
+    if (listA.length != listB.length) {
+      return false;
+    }
+    for (int i = 0; i < listA.length; i++) {
+      if (!itemEqual(listA[i], listB[i])) {
+        return false;
+      }
+    }
+    return true;
+  }
+}