Avoid calling strlen() where possible in base/trace_config

base/trace_event/trace_config_category_filter.h

Index: base/trace_event/trace_config_category_filter.h
diff --git a/base/trace_event/trace_config_category_filter.h b/base/trace_event/trace_config_category_filter.h
index df8c3a5b2a70d3e7a5d4762fa79fa20035905f18..0d7dba0374ebe3767e098bc18ab3a938d336a287 100644
--- a/base/trace_event/trace_config_category_filter.h
+++ b/base/trace_event/trace_config_category_filter.h
@@ -40,13 +40,13 @@ class BASE_EXPORT TraceConfigCategoryFilter {
   // Returns true if at least one category in the list is enabled by this
   // trace config. This is used to determine if the category filters are
   // enabled in the TRACE_* macros.
-  bool IsCategoryGroupEnabled(const char* category_group_name) const;
+  bool IsCategoryGroupEnabled(const StringPiece& category_group_name) const;
 
   // Returns true if the category is enabled according to this trace config.
   // This tells whether a category is enabled from the TraceConfig's
   // perspective. Please refer to IsCategoryGroupEnabled() to determine if a
   // category is enabled from the tracing runtime's perspective.
-  bool IsCategoryEnabled(const char* category_name) const;
+  bool IsCategoryEnabled(const StringPiece& category_name) const;
 
   void ToDict(DictionaryValue* dict) const;