Temporary commit to evaluate perf impact of prototype CPU profiler

base/profiler/cpu_profiler.h

Index: base/profiler/cpu_profiler.h
diff --git a/base/profiler/cpu_profiler.h b/base/profiler/cpu_profiler.h
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+++ b/base/profiler/cpu_profiler.h
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+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_PROFILER_CPU_PROFILER_H_
+#define BASE_PROFILER_CPU_PROFILER_H_
+
+#include <map>
+
+#include "base/base_export.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/strings/string16.h"
+#include "base/synchronization/waitable_event.h"
+#include "base/timer/timer.h"
+
+namespace base {
+
+#if defined(OS_WIN)
+struct StackTraceEntry {
+  DWORD64 rsp;
+  DWORD64 rip;
+  HMODULE module;
+};
+#endif
+
+// CpuProfiler is a prototype of a technique that periodically stops the main
+// thread to samples its stack. It does not do anything useful with the
+// collected information yet; this implementation is for the purposes of
+// determining perf impact of the profiler itself.
+//
+// Currently, this is intended to sample the main thread. It should be allocated
+// on that thread, then Initialize should be called to start the sampling, and
+// Stop called to stop the sampling.
+class BASE_EXPORT CpuProfiler {
+ public:
+  CpuProfiler();
+  ~CpuProfiler();
+
+  void Initialize(const std::map<std::string, std::string>* params);
+  void Stop();
+
+  std::string GetStringParam(const std::string& key) const;
+  int GetIntParam(const std::string& key) const;
+  int64 GetInt64Param(const std::string& key) const;
+
+ private:
+  class SamplingThread;
+  struct SamplingThreadDeleter {
+    void operator() (SamplingThread* thread) const;
+  };
+
+  static bool IsPlatformSupported();
+
+  void SetParams(const std::map<std::string, std::string>& params);
+
+  void OnTimer();
+
+#if defined(OS_WIN)
+  void ProcessStack(StackTraceEntry* stack, int stack_depth);
+
+  HANDLE main_thread_;
+  int main_thread_stack_depth_;
+  StackTraceEntry main_thread_stack_[64];
+
+  std::map<HMODULE, base::string16> modules_;
+#endif
+
+  std::map<std::string, std::string> params_;
+
+  scoped_ptr<SamplingThread, SamplingThreadDeleter> sampling_thread_;
+  PlatformThreadHandle sampling_thread_handle_;
+
+  DISALLOW_COPY_AND_ASSIGN(CpuProfiler);
+};
+
+}  // namespace base
+
+#endif   // BASE_PROFILER_CPU_PROFILER_H_