update the analyzer and analysis server perf tags

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

Index: pkg/analyzer/lib/src/generated/utilities_general.dart
diff --git a/pkg/analyzer/lib/src/generated/utilities_general.dart b/pkg/analyzer/lib/src/generated/utilities_general.dart
index c1413a5af72fc188c91ac8e37087a6e482104b87..35532b4b61d13e455d7c444cc08a1076fc4fb65a 100644
--- a/pkg/analyzer/lib/src/generated/utilities_general.dart
+++ b/pkg/analyzer/lib/src/generated/utilities_general.dart
@@ -91,7 +91,7 @@ abstract class PerformanceTag {
    * Return the [PerformanceTag] that is initially current.  This is intended
    * to track time when the system is performing unknown operations.
    */
-  static PerformanceTag get UNKNOWN => _PerformanceTagImpl.UNKNOWN;
+  static PerformanceTag get unknown => _PerformanceTagImpl.unknown;
 
   /**
    * Create a [PerformanceTag] having the given [label].  A [UserTag] will also
@@ -114,6 +114,12 @@ abstract class PerformanceTag {
   String get label;
 
   /**
+   * Create a child tag of the current tag. The new tag's name will include the
+   * parent's name.
+   */
+  PerformanceTag createChild(String childTagName);
+
+  /**
    * Make this the current tag for the isolate, and return the previous tag.
    */
   PerformanceTag makeCurrent();
@@ -138,9 +144,9 @@ class _PerformanceTagImpl implements PerformanceTag {
   /**
    * The current performance tag for the isolate.
    */
-  static _PerformanceTagImpl current = UNKNOWN;
+  static _PerformanceTagImpl current = unknown;
 
-  static final _PerformanceTagImpl UNKNOWN = new _PerformanceTagImpl('unknown');
+  static final _PerformanceTagImpl unknown = new _PerformanceTagImpl('unknown');
 
   /**
    * A list of all performance tags that have been created so far.
@@ -171,6 +177,11 @@ class _PerformanceTagImpl implements PerformanceTag {
   String get label => userTag.label;
 
   @override
+  PerformanceTag createChild(String childTagName) {
+    return new _PerformanceTagImpl('$label.$childTagName');
+  }
+
+  @override
   PerformanceTag makeCurrent() {
     if (identical(this, current)) {
       return current;