Trace category groups and category filter.

content/public/browser/trace_controller.h

Index: content/public/browser/trace_controller.h
diff --git a/content/public/browser/trace_controller.h b/content/public/browser/trace_controller.h
index 6bdff6c0c13d7c1c0d51a8bd6b7f8282d8bc42b5..5634bb9ed269027ffe29eb941091a3fd288144fd 100644
--- a/content/public/browser/trace_controller.h
+++ b/content/public/browser/trace_controller.h
@@ -30,16 +30,17 @@ class TraceController {
   //   or if another subscriber is tracing,
   //   BeginTracing will return false meaning it failed.
   //
-  // |categories| is a comma-delimited list of category wildcards.
-  // A category can have an optional '-' prefix to make it an excluded category.
+  // |tag_patterns| is a comma-delimited list of tag category wildcards.
+  // A tag pattern can have an optional '-' prefix to exclude categories that
+  // contain a matching tag pattern.
   // All the same rules apply above, so for example, having both included and
-  // excluded categories in the same list would not be supported.
+  // excluded tag_patterns in the same list would not be supported.
   //
   // Example: BeginTracing("test_MyTest*");
   // Example: BeginTracing("test_MyTest*,test_OtherStuff");
-  // Example: BeginTracing("-excluded_category1,-excluded_category2");
+  // Example: BeginTracing("-excluded_category_tag1,-excluded_category_tag2");
   virtual bool BeginTracing(TraceSubscriber* subscriber,
-                            const std::string& categories) = 0;
+                            const std::string& tag_patterns) = 0;
 
   // Called by browser process to stop tracing events on all processes.
   //