Remove references to AnalysisDriver from the plugin mixin classes

pkg/analyzer_plugin/lib/plugin/plugin.dart

Index: pkg/analyzer_plugin/lib/plugin/plugin.dart
diff --git a/pkg/analyzer_plugin/lib/plugin/plugin.dart b/pkg/analyzer_plugin/lib/plugin/plugin.dart
index fc9921e18382d7f5f413610d7a522cbd686aef54..0848d04f79a545c22e9d374673a72f1ac044e9bc 100644
--- a/pkg/analyzer_plugin/lib/plugin/plugin.dart
+++ b/pkg/analyzer_plugin/lib/plugin/plugin.dart
@@ -191,6 +191,17 @@ abstract class ServerPlugin {
   AnalysisDriverGeneric createAnalysisDriver(ContextRoot contextRoot);
 
   /**
+   * Return the driver being used to analyze the file with the given [path].
+   */
+  AnalysisDriverGeneric driverForPath(String path) {

[mfairhurst, 2017/07/05 22:50:51]

Isn't this also a public usage of a private API?

[Brian Wilkerson, 2017/07/05 23:06:49]

Yes, it is. But it seemed like an expedient step toward the goal to get all of
the references out of the mixins at the cost of adding one more to ServerPlugin.
I might regret it, but...

+    ContextRoot contextRoot = contextRootContaining(path);
+    if (contextRoot == null) {
+      return null;
+    }
+    return driverMap[contextRoot];
+  }
+
+  /**
    * Handle an 'analysis.getNavigation' request.
    */
   Future<AnalysisGetNavigationResult> handleAnalysisGetNavigation(