[ETW Export] Add polling for ETW keyword.

base/trace_event/trace_event_etw_export_win.cc

Index: base/trace_event/trace_event_etw_export_win.cc
diff --git a/base/trace_event/trace_event_etw_export_win.cc b/base/trace_event/trace_event_etw_export_win.cc
index 47e6353704764112b98cef7d794b08f9726758bb..01529875035b337f6aafb9fe8c7d2a46619ddfdb 100644
--- a/base/trace_event/trace_event_etw_export_win.cc
+++ b/base/trace_event/trace_event_etw_export_win.cc
@@ -90,6 +90,9 @@ const char* disabled_other_events_group_name =
     "__DISABLED_OTHER_EVENTS";  // 0x4000000000000000
 uint64 other_events_keyword_bit = 1ULL << 61;
 uint64 disabled_other_events_keyword_bit = 1ULL << 62;
+
+// Time between checks for ETW keyword changes (in milliseconds).
+unsigned int kUpdateTimerDelayMs = 1000;
 }  // namespace
 
 // Redirector function for EventRegister. Called by macros in
@@ -171,6 +174,11 @@ void TraceEventETWExport::DisableETWExport() {
 }
 
 // static
+bool TraceEventETWExport::IsETWExportEnabled() {
+  return (GetInstance() && GetInstance()->etw_export_enabled_);

[brucedawson, 2015/06/26 22:24:24]

If you move this and change it in the same CL then the change is very hard to
see. Consider leaving it in its original location.

A separate CL to move it (before or after) would also work.

+}
+
+// static
 void TraceEventETWExport::AddEvent(
     char phase,
     const unsigned char* category_group_enabled,
@@ -297,10 +305,6 @@ void TraceEventETWExport::AddCustomEvent(const char* name,
                         arg_value_2, arg_name_3, arg_value_3);
 }
 
-void TraceEventETWExport::Resurrect() {
-  StaticMemorySingletonTraits<TraceEventETWExport>::Resurrect();
-}
-
 // static
 bool TraceEventETWExport::IsCategoryGroupEnabled(
     const char* category_group_name) {
@@ -324,21 +328,36 @@ bool TraceEventETWExport::IsCategoryGroupEnabled(
   return false;
 }
 
-void TraceEventETWExport::UpdateEnabledCategories() {
+// static
+void TraceEventETWExport::StartKeywordUpdateTimer() {
+  if (IsETWExportEnabled()) {
+    GetInstance()->keyword_update_timer_.Start(
+        FROM_HERE, base::TimeDelta::FromMilliseconds(kUpdateTimerDelayMs),
+        base::Bind(&TraceEventETWExport::KeywordUpdateTimerCallback));
+  }
+}
+
+void TraceEventETWExport::Resurrect() {
+  StaticMemorySingletonTraits<TraceEventETWExport>::Resurrect();
+}
+
+bool TraceEventETWExport::UpdateEnabledCategories() {
+  if (etw_match_any_keyword_ == CHROME_Context.MatchAnyKeyword)
+    return false;
+
   // If the keyword has changed, update each category.
   // Chrome_Context.MatchAnyKeyword is set by UIforETW (or other ETW trace
   // recording tools) using the ETW infrastructure. This value will be set in
   // all Chrome processes that have registered their ETW provider.
-  if (etw_match_any_keyword_ != CHROME_Context.MatchAnyKeyword) {
-    etw_match_any_keyword_ = CHROME_Context.MatchAnyKeyword;
-    for (int i = 0; i < ARRAYSIZE(filtered_event_group_names); i++) {
-      if (etw_match_any_keyword_ & (1ULL << i)) {
-        categories_status_[filtered_event_group_names[i]] = true;
-      } else {
-        categories_status_[filtered_event_group_names[i]] = false;
-      }
+  etw_match_any_keyword_ = CHROME_Context.MatchAnyKeyword;
+  for (int i = 0; i < ARRAYSIZE(filtered_event_group_names); i++) {
+    if (etw_match_any_keyword_ & (1ULL << i)) {
+      categories_status_[filtered_event_group_names[i]] = true;
+    } else {
+      categories_status_[filtered_event_group_names[i]] = false;
     }
   }
+
   // Also update the two default categories.
   if (etw_match_any_keyword_ & other_events_keyword_bit) {
     categories_status_[other_events_group_name] = true;
@@ -350,6 +369,8 @@ void TraceEventETWExport::UpdateEnabledCategories() {
   } else {
     categories_status_[disabled_other_events_group_name] = false;
   }
+
+  return true;
 }
 
 bool TraceEventETWExport::IsCategoryEnabled(const char* category_name) const {
@@ -371,5 +392,13 @@ bool TraceEventETWExport::IsCategoryEnabled(const char* category_name) const {
   }
 }
 
+// static
+void TraceEventETWExport::KeywordUpdateTimerCallback() {
+  DCHECK(GetInstance());
+  if (IsETWExportEnabled()) {
+    if (GetInstance()->UpdateEnabledCategories())
+      TraceLog::GetInstance()->UpdateCategoryGroupEnabledFlags();
+  }
+}
 }  // namespace trace_event
 }  // namespace base