Move trace_event and associated files to webrtc/base.
Also starting to use TRACE_EVENT from thread.cc in webrtc/base, to track Invoke() calls.

BUG=
R=magjed@webrtc.org, tina.legrand@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/42769004

Cr-Commit-Position: refs/heads/master@{#8755}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8755 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/base/event_tracer.cc b/webrtc/base/event_tracer.cc
new file mode 100644
index 0000000..5c6d39f
--- /dev/null
+++ b/webrtc/base/event_tracer.cc
@@ -0,0 +1,60 @@
+/*
+ *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/base/event_tracer.h"
+
+namespace webrtc {
+
+namespace {
+
+GetCategoryEnabledPtr g_get_category_enabled_ptr = 0;
+AddTraceEventPtr g_add_trace_event_ptr = 0;
+
+}  // namespace
+
+void SetupEventTracer(GetCategoryEnabledPtr get_category_enabled_ptr,
+                      AddTraceEventPtr add_trace_event_ptr) {
+  g_get_category_enabled_ptr = get_category_enabled_ptr;
+  g_add_trace_event_ptr = add_trace_event_ptr;
+}
+
+// static
+const unsigned char* EventTracer::GetCategoryEnabled(const char* name) {
+  if (g_get_category_enabled_ptr)
+    return g_get_category_enabled_ptr(name);
+
+  // A string with null terminator means category is disabled.
+  return reinterpret_cast<const unsigned char*>("\0");
+}
+
+// static
+void EventTracer::AddTraceEvent(char phase,
+                                const unsigned char* category_enabled,
+                                const char* name,
+                                unsigned long long id,
+                                int num_args,
+                                const char** arg_names,
+                                const unsigned char* arg_types,
+                                const unsigned long long* arg_values,
+                                unsigned char flags) {
+  if (g_add_trace_event_ptr) {
+    g_add_trace_event_ptr(phase,
+                          category_enabled,
+                          name,
+                          id,
+                          num_args,
+                          arg_names,
+                          arg_types,
+                          arg_values,
+                          flags);
+  }
+}
+
+}  // namespace webrtc