Restore skipping of default categories.

Looks like the code to skip the default categories, and the unit test,
were removed by accident in a merge. Restoring so the category selection
dialog works correctly.

BUG=195661

Review URL: https://chromiumcodereview.appspot.com/14320028

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@195295 0039d316-1c4b-4281-b951-d872f2087c98

base/debug/trace_event_impl.cc

@@ -861,7 +861,7 @@ const unsigned char* TraceLog::GetCategoryGroupEnabledInternal(
 void TraceLog::GetKnownCategoryGroups(
     std::vector<std::string>* category_groups) {
   AutoLock lock(lock_);
-  for (int i = 0; i < g_category_index; i++)
+  for (int i = g_num_builtin_categories; i < g_category_index; i++)
     category_groups->push_back(g_category_groups[i]);
 }
 

base/debug/trace_event_unittest.cc

@@ -900,6 +900,9 @@ TEST_F(TraceEventTestFixture, Categories) {
                         cat_groups.end(), "c5,c6") != cat_groups.end());
   EXPECT_TRUE(std::find(cat_groups.begin(),
                         cat_groups.end(), "c7,c8") != cat_groups.end());
+  // Make sure metadata isn't returned.
+  EXPECT_TRUE(std::find(cat_groups.begin(),
+                        cat_groups.end(), "__metadata") == cat_groups.end());
 
   const std::vector<std::string> empty_categories;
   std::vector<std::string> included_categories;