Added a whitelist for trace events that are known to be PII-less.

base/trace_event/trace_event_impl.cc

Index: base/trace_event/trace_event_impl.cc
diff --git a/base/trace_event/trace_event_impl.cc b/base/trace_event/trace_event_impl.cc
index 396bcc23a0417beebf9bc507386643488eeba399..172392b6a7dd9f89699fd35dd068ec1079ea90e4 100644
--- a/base/trace_event/trace_event_impl.cc
+++ b/base/trace_event/trace_event_impl.cc
@@ -68,6 +68,7 @@ const char kRecordAsMuchAsPossible[] = "record-as-much-as-possible";
 const char kTraceToConsole[] = "trace-to-console";
 const char kEnableSampling[] = "enable-sampling";
 const char kEnableSystrace[] = "enable-systrace";
+const char kEnableArgsWhitelist[] = "enable-args-whitelist";
 
 // Controls the number of trace events we will buffer in-memory
 // before throwing them away.
@@ -1014,6 +1015,8 @@ bool TraceOptions::SetFromString(const std::string& options_string) {
       enable_sampling = true;
     } else if (*iter == kEnableSystrace) {
       enable_systrace = true;
+    } else if (*iter == kEnableArgsWhitelist) {
+      enable_args_whitelist = true;
     } else {
       return false;
     }
@@ -1043,6 +1046,8 @@ std::string TraceOptions::ToString() const {
     ret = ret + "," + kEnableSampling;
   if (enable_systrace)
     ret = ret + "," + kEnableSystrace;
+  if (enable_args_whitelist)
+    ret = ret + "," + kEnableArgsWhitelist;
   return ret;
 }
 
@@ -1500,6 +1505,7 @@ void TraceLog::SetEnabled(const CategoryFilter& category_filter,
 void TraceLog::SetEventFilterPredicate(
     const TraceEvent::EventFilterPredicate& event_filter_predicate) {
   AutoLock lock(lock_);
+  DCHECK(!event_filter_predicate.is_null());
   event_filter_predicate_ = event_filter_predicate;
 }
 
@@ -1507,6 +1513,8 @@ TraceLog::InternalTraceOptions TraceLog::GetInternalOptionsFromTraceOptions(
     const TraceOptions& options) {
   InternalTraceOptions ret =
       options.enable_sampling ? kInternalEnableSampling : kInternalNone;
+  if (options.enable_args_whitelist)
+    ret |= kInternalEnableArgsWhitelist;
   switch (options.record_mode) {
     case RECORD_UNTIL_FULL:
       return ret | kInternalRecordUntilFull;
@@ -1530,6 +1538,7 @@ TraceOptions TraceLog::GetCurrentTraceOptions() const {
   TraceOptions ret;
   InternalTraceOptions option = trace_options();
   ret.enable_sampling = (option & kInternalEnableSampling) != 0;
+  ret.enable_args_whitelist = (option & kInternalEnableArgsWhitelist) != 0;
   if (option & kInternalRecordUntilFull)
     ret.record_mode = RECORD_UNTIL_FULL;
   else if (option & kInternalRecordContinuously)