Histograms - Support histograms for Plugins, GPU

content/browser/histogram_controller.h

+// Copyright (c) 2012 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 CONTENT_BROWSER_HISTOGRAM_CONTROLLER_H_
+#define CONTENT_BROWSER_HISTOGRAM_CONTROLLER_H_
+
+#include <string>
+#include <vector>
+
+#include "base/memory/singleton.h"
+
+namespace content {
+
+class HistogramSubscriber;
+
+// HistogramController is used on the browser process to collect histogram data.
+// Only the browser UI thread is allowed to interact with the
+// HistogramController object.
+class HistogramController {
+ public:
+  // Returns the HistogramController object for the current process, or NULL if
+  // none.
+  static HistogramController* GetInstance();
+
+  // Normally instantiated when the child process is launched. Only one instance
+  // should be created per process.
+  HistogramController();
+  virtual ~HistogramController();
+
+  // Register the subscriber so that it will be called when for example
+  // OnHistogramDataCollected is returning histogram data from a child process.
+  // This is called on UI thread.
+  void Register(HistogramSubscriber* subscriber);
+
+  // Unregister the subscriber so that it will not be called when for example
+  // OnHistogramDataCollected is returning histogram data from a child process.
+  // Safe to call even if caller is not the current subscriber.
+  void Unregister(const HistogramSubscriber* subscriber);
+
+  // Contact all processes and get their histogram data.
+  void GetHistogramData(int sequence_number);
+
+  // Notify the |subscriber_| that it should expect at least |pending_processes|
+  // additional calls to OnHistogramDataCollected().  OnPendingProcess() may be
+  // called repeatedly; the last call will have |end| set to true, indicating
+  // that there is no longer a possibility for the count of pending processes to
+  // increase.  This is called on the UI thread.
+  void OnPendingProcesses(int sequence_number, int pending_processes, bool end);
+
+  // Send the |histogram| back to the |subscriber_|.
+  // This can be called from any thread.
+  void OnHistogramDataCollected(
+      int sequence_number,
+      const std::vector<std::string>& pickled_histograms);
+
+ private:
+  friend struct DefaultSingletonTraits<HistogramController>;
+
+  // Contact child processes and get their histogram data.
+  void GetHistogramDataFromChildProcesses(int sequence_number);
+
+  HistogramSubscriber* subscriber_;
+
+  DISALLOW_COPY_AND_ASSIGN(HistogramController);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_HISTOGRAM_CONTROLLER_H_