tracing: Display all categories in about:tracing UI.

about:tracing UI calls TraceLog::GetKnownCategoryGroups() to get categories to
display in "Record" dialog. This function assumes that built-in categories
shouldn't be displayed.

However, the CL https://crrev.com/c/1251361 made almost all categories built-in,
thus a majority of categories isn't displayed in the UI.

This CL fixes this by narrowing the list of non-displayed categories to "meta"
categories.

Bug: 708990
Change-Id: Ic8ccfa396e890983afda96a20ebfe00557f319a9
Reviewed-on: https://chromium-review.googlesource.com/c/1341909Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Reviewed-by: Primiano Tucci <primiano@chromium.org>
Commit-Queue: Alexandr Ilin <alexilin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609344}

base/trace_event/category_registry.cc

@@ -122,9 +122,9 @@ const TraceCategory* CategoryRegistry::GetCategoryByStatePtr(
 }
 
 // static
-bool CategoryRegistry::IsBuiltinCategory(const TraceCategory* category) {
+bool CategoryRegistry::IsMetaCategory(const TraceCategory* category) {
   DCHECK(IsValidCategoryPtr(category));
-  return category < &categories_[BuiltinCategories::Size()];
+  return category <= kCategoryMetadata;
 }
 
 // static

base/trace_event/category_registry.h

@@ -83,7 +83,9 @@ class BASE_EXPORT CategoryRegistry {
 #endif
   }
 
-  static bool IsBuiltinCategory(const TraceCategory*);
+  // Returns whether |category| points at one of the meta categories that
+  // shouldn't be displayed in the tracing UI.
+  static bool IsMetaCategory(const TraceCategory* category);
 
  private:
   friend class TraceCategoryTest;

base/trace_event/trace_category_unittest.cc

@@ -112,10 +112,10 @@ TEST_F(TraceCategoryTest, Basic) {
   int num_test_categories_seen = 0;
   for (const TraceCategory& cat : GetAllCategories()) {
     if (strcmp(cat.name(), kMetadataName) == 0)
-      ASSERT_TRUE(CategoryRegistry::IsBuiltinCategory(&cat));
+      ASSERT_TRUE(CategoryRegistry::IsMetaCategory(&cat));
 
     if (strncmp(cat.name(), "__test_basic_", 13) == 0) {
-      ASSERT_FALSE(CategoryRegistry::IsBuiltinCategory(&cat));
+      ASSERT_FALSE(CategoryRegistry::IsMetaCategory(&cat));
       num_test_categories_seen++;
     }
   }

base/trace_event/trace_log.cc

@@ -562,7 +562,7 @@ void TraceLog::CreateFiltersForTraceConfig() {
 void TraceLog::GetKnownCategoryGroups(
     std::vector<std::string>* category_groups) {
   for (const auto& category : CategoryRegistry::GetAllCategories()) {
-    if (!CategoryRegistry::IsBuiltinCategory(&category))
+    if (!CategoryRegistry::IsMetaCategory(&category))
       category_groups->push_back(category.name());
   }
 }