Add ExitFunnel to prepare for instrumenting browser exits.

components/browser_watcher/exit_funnel_win.h

Index: components/browser_watcher/exit_funnel_win.h
diff --git a/components/browser_watcher/exit_funnel_win.h b/components/browser_watcher/exit_funnel_win.h
new file mode 100644
index 0000000000000000000000000000000000000000..6b490da04aba66eefd922c13d4ef3ed52dcb1471
--- /dev/null
+++ b/components/browser_watcher/exit_funnel_win.h
@@ -0,0 +1,50 @@
+// Copyright (c) 2014 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 COMPONENTS_BROWSER_WATCHER_EXIT_FUNNEL_WIN_H_
+#define COMPONENTS_BROWSER_WATCHER_EXIT_FUNNEL_WIN_H_
+
+#include "base/macros.h"
+#include "base/process/process_handle.h"
+#include "base/strings/string16.h"
+#include "base/win/registry.h"
+
+namespace browser_watcher {
+
+// A wrapper class that takes care of persistently recording a trace of named,
+// timed events in registry, associated with a process instance. This allows
+// reconstructing and reporting an event trace on a subsequent launch.
+// The event trace is stored in registry under a new key named
+// <pid>-<uniquifier>, where each event is a value named after the event, with
+// an associated QWORD value noting the event time.
+class ExitFunnel {
+ public:
+  ExitFunnel();
+  ~ExitFunnel();
+
+  // Initializes the exit funnel with |registry_path| and |process|.
+  // |process| must be open for PROCESS_QUERY_INFORMATION at least.
+  // Returns false on failure to create or open the registry path corresponding
+  // to |process|.
+  bool Init(const base::char16* registry_path, base::ProcessHandle process);
+
+  // Records |event_name| at the current time in the registry for the process
+  // this instance is associated with. Returns false on failure to record the
+  // event.
+  bool RecordEvent(const base::char16* event_name);
+
+  // Records |event_name| at the current time in the registry at |registry_path|
+  // for this process.
+  static bool RecordSingleEvent(const base::char16* registry_path,
+                                const base::char16* event_name);
+
+ private:
+  base::win::RegKey key_;
+
+  DISALLOW_COPY_AND_ASSIGN(ExitFunnel);
+};
+
+}  // namespace browser_watcher
+
+#endif  // COMPONENTS_BROWSER_WATCHER_EXIT_FUNNEL_WIN_H_