initial import of Chrome's trace_event into skia framework

src/utils/SkEventTracer.cpp

+/*
+ * Copyright 2013 Google Inc.

[mtklein, 2014/01/29 20:57:55]

I bet you can bump this to 2014 now.

+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkEventTracer.h"
+#include "SkOnce.h"
+
+namespace skia {
+namespace tracing {
+
+class SkDefaultEventTracer: public SkEventTracer {
+    virtual TraceEventHandle 

[mtklein, 2014/01/29 20:57:55]

Doesn't hurt to tack on SK_OVERRIDE to these.

You don't really need virtual unless you're planning on subclassing
SkDefaultEventTracer, but I guess they don't hurt.

+        AddTraceEvent(char phase,
+                      const unsigned char* categoryEnabledFlag,
+                      const char* name,
+                      unsigned long long id,
+                      int numArgs,
+                      const char** argNames,
+                      const unsigned char* argTypes,
+                      const unsigned long long* argValues,
+                      unsigned char flags) { return 0; }
+    
+    virtual void 
+        UpdateTraceEventDuration(const unsigned char* categoryEnabledFlag, 
+                                 const char* name, 
+                                 tracing::TraceEventHandle) {};
+
+    virtual const unsigned char* GetCategoryGroupEnabled(const char* name) {
+        static unsigned char no = 1;
+        return &no;
+    };
+    virtual const char* GetCategoryGroupName(
+      const unsigned char* category_group_enabled) {
+        static const char* dummy = "dummy";
+        return dummy;
+    };
+};
+
+SkEventTracer *SkEventTracer::_instance;
+
+static void intiailize_default_tracer(void**) {

[mtklein, 2014/01/29 20:57:55]

If you're not going to use the argument, we usually make it int and pass 0.  I
guess you can call it void****** if you like.

+    SkEventTracer::SetInstance(SkNEW(SkDefaultEventTracer));
+}
+
+SkEventTracer *SkEventTracer::GetInstance() {

[mtklein, 2014/01/29 20:57:55]

We almost always put the * on the left.

+    SK_DECLARE_STATIC_ONCE(once);
+    SkOnce(&once, intiailize_default_tracer, (void **) NULL);
+    SkASSERT(NULL != SkEventTracer::_instance);
+    return SkEventTracer::_instance;
+}
+
+}

[mtklein, 2014/01/29 20:57:55]

If you keep the namespaces, can you add 

} // namespace tracing
} // namespace skia

?

+}