Add DeclaredVariables to AnalysisDriver.

pkg/analyzer/lib/context/declared_variables.dart

Index: pkg/analyzer/lib/context/declared_variables.dart
diff --git a/pkg/analyzer/lib/context/declared_variables.dart b/pkg/analyzer/lib/context/declared_variables.dart
index 50c47ddca372dfdf2eb535cce628510abf76490a..5f6d6f1d580a0dd156183924201d80ff96cff261 100644
--- a/pkg/analyzer/lib/context/declared_variables.dart
+++ b/pkg/analyzer/lib/context/declared_variables.dart
@@ -28,6 +28,13 @@ class DeclaredVariables {
   Iterable<String> get variableNames => _declaredVariables.keys;
 
   /**
+   * Add all variables of [other] to this object.
+   */
+  void addAll(DeclaredVariables other) {
+    _declaredVariables.addAll(other._declaredVariables);
+  }
+
+  /**
    * Define a variable with the given [name] to have the given [value].
    */
   void define(String name, String value) {