[Cleanup] List trace categories through script as shown by trace record dialog

tools/profile_chrome/chrome_controller.py

Index: tools/profile_chrome/chrome_controller.py
diff --git a/tools/profile_chrome/chrome_controller.py b/tools/profile_chrome/chrome_controller.py
index 91c2504a54c4e34583644db055ad6cd543dd6fb7..c48c53b103145db5b230062bb094c814f1548bff 100644
--- a/tools/profile_chrome/chrome_controller.py
+++ b/tools/profile_chrome/chrome_controller.py
@@ -47,14 +47,15 @@ class ChromeTracingController(controllers.BaseController):
       raise RuntimeError('Performance trace category list marker not found. '
                          'Is the correct version of the browser running?')
 
-    record_categories = []
-    disabled_by_default_categories = []
+    record_categories = set()

[dsinclair, 2014/11/10 14:10:13]

Does a set() work the same way as [] for access? Will the callers of
GetCategories be expecting an array and having a set instead cause issues?

[Sami, 2014/11/10 14:39:45]

You can iterate over sets the same way as lists (for x in s), but indexing isn't
supported so they're not exactly compatible. We could hide the fact that we're
dealing with sets by converting them to lists instead:

    return list(record_categories), list(disabled_by_default_categories)

+    disabled_by_default_categories = set()
     json_data = json.loads(json_category_list)['traceCategoriesList']
     for item in json_data:
-      if item.startswith('disabled-by-default'):
-        disabled_by_default_categories.append(item)
-      else:
-        record_categories.append(item)
+      for category in item.split(','):
+        if category.startswith('disabled-by-default'):
+          disabled_by_default_categories.add(category)
+        else:
+          record_categories.add(category)
 
     return record_categories, disabled_by_default_categories