Add a mode flag to the tracing framework.

base/debug/trace_event_impl.cc

Index: base/debug/trace_event_impl.cc
diff --git a/base/debug/trace_event_impl.cc b/base/debug/trace_event_impl.cc
index cbcf54b81c6aac08b08d5f71fb6796f6869b84de..d5a88edd3e5f0c5db26e25774c62a52bbab41176 100644
--- a/base/debug/trace_event_impl.cc
+++ b/base/debug/trace_event_impl.cc
@@ -348,10 +348,28 @@ TraceLog* TraceLog::GetInstance() {
   return Singleton<TraceLog, StaticMemorySingletonTraits<TraceLog> >::get();
 }
 
+// static
+TraceLog::TraceMode TraceLog::TraceModeFromString(const std::string& str) {
+  if (str == "until_full")
+    return UNTIL_FULL;
+  return UNTIL_FULL;
+}
+
+// static
+const std::string TraceLog::StringFromTraceMode(TraceMode mode) {
+  switch(mode) {
+    case UNTIL_FULL:
+      return "until_full";
+    default:
+      return "";
+  }
+}
+
 TraceLog::TraceLog()
     : enable_count_(0),
       dispatching_to_observer_list_(false),
-      watch_category_(NULL) {
+      watch_category_(NULL),
+      trace_mode_(UNTIL_FULL) {
   // Trace is enabled or disabled on one thread while other threads are
   // accessing the enabled flag. We don't care whether edge-case events are
   // traced or not, so we allow races on the enabled flag to keep the trace
@@ -478,10 +496,15 @@ void TraceLog::GetKnownCategories(std::vector<std::string>* categories) {
 }
 
 void TraceLog::SetEnabled(const std::vector<std::string>& included_categories,
-                          const std::vector<std::string>& excluded_categories) {
+                          const std::vector<std::string>& excluded_categories,
+                          TraceMode mode) {
   AutoLock lock(lock_);
 
   if (enable_count_++ > 0) {
+    if (mode != trace_mode_) {
+      DLOG(ERROR) << "Attemting to re-enable tracing with a different mode.";
+    }
+
     // Tracing is already enabled, so just merge in enabled categories.
     // We only expand the set of enabled categories upon nested SetEnable().
     if (!included_categories_.empty() && !included_categories.empty()) {
@@ -497,6 +520,7 @@ void TraceLog::SetEnabled(const std::vector<std::string>& included_categories,
     }
     return;
   }
+  trace_mode_ = mode;
 
   if (dispatching_to_observer_list_) {
     DLOG(ERROR) <<
@@ -520,7 +544,7 @@ void TraceLog::SetEnabled(const std::vector<std::string>& included_categories,
     EnableMatchingCategories(excluded_categories_, 0, CATEGORY_ENABLED);
 }
 
-void TraceLog::SetEnabled(const std::string& categories) {
+void TraceLog::SetEnabled(const std::string& categories, TraceMode mode) {
   std::vector<std::string> included, excluded;
   // Tokenize list of categories, delimited by ','.
   StringTokenizer tokens(categories, ",");
@@ -538,7 +562,7 @@ void TraceLog::SetEnabled(const std::string& categories) {
     else
       excluded.push_back(category);
   }
-  SetEnabled(included, excluded);
+  SetEnabled(included, excluded, mode);
 }
 
 void TraceLog::GetEnabledTraceCategories(
@@ -577,9 +601,9 @@ void TraceLog::SetDisabled() {
   AddThreadNameMetadataEvents();
 }
 
-void TraceLog::SetEnabled(bool enabled) {
+void TraceLog::SetEnabled(bool enabled, TraceMode mode) {
   if (enabled)
-    SetEnabled(std::vector<std::string>(), std::vector<std::string>());
+    SetEnabled(std::vector<std::string>(), std::vector<std::string>(), mode);
   else
     SetDisabled();
 }