Added a trace option for whitewashing trace args against a known-PII-less list.

base/trace_event/trace_event_impl.h

Index: base/trace_event/trace_event_impl.h
diff --git a/base/trace_event/trace_event_impl.h b/base/trace_event/trace_event_impl.h
index 33a85c9b6ce854f4e6b6cde748fe6abca8a015d2..30b2a63df2ddfe732a0f3930e81a033143428d50 100644
--- a/base/trace_event/trace_event_impl.h
+++ b/base/trace_event/trace_event_impl.h
@@ -122,7 +122,10 @@ class BASE_EXPORT TraceEvent {
   void UpdateDuration(const TimeTicks& now, const TimeTicks& thread_now);
 
   // Serialize event data to JSON
-  void AppendAsJSON(std::string* out) const;
+  typedef base::Callback<bool(const char* category_group_name,
+                              const char* event_name)> EventFilterPredicate;
+  void AppendAsJSON(std::string* out,
+                    const EventFilterPredicate& event_filter_predicate) const;
   void AppendPrettyPrinted(std::ostringstream* out) const;
 
   static void AppendValueAsJSON(unsigned char type,
@@ -383,12 +386,14 @@ struct BASE_EXPORT TraceOptions {
   TraceOptions()
       : record_mode(RECORD_UNTIL_FULL),
         enable_sampling(false),
-        enable_systrace(false) {}
+        enable_systrace(false),
+        enable_args_whitelist(false) {}
 
   explicit TraceOptions(TraceRecordMode record_mode)
       : record_mode(record_mode),
         enable_sampling(false),
-        enable_systrace(false) {}
+        enable_systrace(false),
+        enable_args_whitelist(false) {}

[nduca, 2015/05/01 03:09:03]

Should devtools protocol support this enable_args_whitelist? i was good to lg
the rest of this patch except for my indecision around whether anytime we add a
trace option we should update devtools protocol to accept it.

i had originally requested that the enable_Args_whitelist changew as a separate
patch so that i could add pavel to the codereview to ask for his advice.

i'd still kinda like to do that. we could add him to this total patch, but the
"proper" thing to do codereview wise is to have a patch that is one logical
thought at a time. in this case, we still have two thoughts in the patch: one
about predicate, one about the new option. so thats making this hard to give
good review to.

help, need advice on how to proceed.

 
   // |options_string| is a comma-delimited list of trace options.
   // Possible options are: "record-until-full", "record-continuously",
@@ -419,6 +424,7 @@ struct BASE_EXPORT TraceOptions {
   TraceRecordMode record_mode;
   bool enable_sampling;
   bool enable_systrace;
+  bool enable_args_whitelist;
 };
 
 struct BASE_EXPORT TraceLogStatus {
@@ -532,6 +538,8 @@ class BASE_EXPORT TraceLog {
   void SetEventCallbackEnabled(const CategoryFilter& category_filter,
                                EventCallback cb);
   void SetEventCallbackDisabled();
+  void SetEventFilterPredicate(
+      const TraceEvent::EventFilterPredicate& event_filter_predicate);
 
   // Flush all collected events to the given output callback. The callback will
   // be called one or more times either synchronously or asynchronously from
@@ -717,9 +725,10 @@ class BASE_EXPORT TraceLog {
   // is called for the flush of the current |logged_events_|.
   void FlushCurrentThread(int generation);
   // Usually it runs on a different thread.
-  static void ConvertTraceEventsToTraceFormat(
+  void ConvertTraceEventsToTraceFormat(
       scoped_ptr<TraceBuffer> logged_events,
-      const TraceLog::OutputCallback& flush_output_callback);
+      const TraceLog::OutputCallback& flush_output_callback,
+      const TraceEvent::EventFilterPredicate& event_filter_predicate);
   void FinishFlush(int generation);
   void OnFlushTimeout(int generation);
 
@@ -746,6 +755,7 @@ class BASE_EXPORT TraceLog {
   static const InternalTraceOptions kInternalEchoToConsole;
   static const InternalTraceOptions kInternalEnableSampling;
   static const InternalTraceOptions kInternalRecordAsMuchAsPossible;
+  static const InternalTraceOptions kInternalEnableArgsWhitelist;
 
   // This lock protects TraceLog member accesses (except for members protected
   // by thread_info_lock_) from arbitrary threads.
@@ -809,6 +819,7 @@ class BASE_EXPORT TraceLog {
 
   // Set when asynchronous Flush is in progress.
   OutputCallback flush_output_callback_;
+  TraceEvent::EventFilterPredicate event_filter_predicate_;
   scoped_refptr<MessageLoopProxy> flush_message_loop_proxy_;
   subtle::AtomicWord generation_;
   bool use_worker_thread_;