Add context information to driver and add hooks for plugin management

pkg/analysis_server/lib/src/services/completion/dart/arglist_contributor.dart

Index: pkg/analysis_server/lib/src/services/completion/dart/arglist_contributor.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart/arglist_contributor.dart b/pkg/analysis_server/lib/src/services/completion/dart/arglist_contributor.dart
index 6eb3bbe89f40d7d7e1d1194844d34f7ff59969f9..579b7b8662c16a1b621dddba7de8b6008a459b3e 100644
--- a/pkg/analysis_server/lib/src/services/completion/dart/arglist_contributor.dart
+++ b/pkg/analysis_server/lib/src/services/completion/dart/arglist_contributor.dart
@@ -286,19 +286,6 @@ class ArgListContributor extends DartCompletionContributor {
     }
   }
 
-  String _getDefaultValue(ParameterElement param, IdeOptions options) {
-    if (options?.generateFlutterWidgetChildrenBoilerPlate == true) {
-      Element element = param.enclosingElement;
-      if (element is ConstructorElement) {
-        if (isFlutterWidget(element.enclosingElement) &&
-            param.name == 'children') {
-          return getDefaultStringParameterValue(param);
-        }
-      }
-    }
-    return null;
-  }
-
   void _addSuggestions(Iterable<ParameterElement> parameters) {
     if (parameters == null || parameters.length == 0) {
       return;
@@ -322,6 +309,19 @@ class ArgListContributor extends DartCompletionContributor {
     }
   }
 
+  String _getDefaultValue(ParameterElement param, IdeOptions options) {
+    if (options?.generateFlutterWidgetChildrenBoilerPlate == true) {
+      Element element = param.enclosingElement;
+      if (element is ConstructorElement) {
+        if (isFlutterWidget(element.enclosingElement) &&
+            param.name == 'children') {
+          return getDefaultStringParameterValue(param);
+        }
+      }
+    }
+    return null;
+  }
+
   /**
    * If the given [comment] is not `null`, fill the [suggestion] documentation
    * fields.