Add timing info for file IO into Dart based analyzer.

pkg/analyzer/lib/src/generated/engine.dart

Index: pkg/analyzer/lib/src/generated/engine.dart
diff --git a/pkg/analyzer/lib/src/generated/engine.dart b/pkg/analyzer/lib/src/generated/engine.dart
index b64bdc1a1f4a404b14abe8be17e30d86f2878b37..ff1bebc61aa399f467402d25a3aa9bbf89c829a9 100644
--- a/pkg/analyzer/lib/src/generated/engine.dart
+++ b/pkg/analyzer/lib/src/generated/engine.dart
@@ -8601,6 +8601,11 @@ class PerformanceStatistics {
   static TimeCounter angular = new TimeCounter();
 
   /**
+   * The [TimeCounter] for time spent in reading files.
+   */
+  static TimeCounter io = new TimeCounter();
+
+  /**
    * The [TimeCounter] for time spent in scanning.
    */
   static TimeCounter scan = new TimeCounter();