Added a debug info UI for Blimp

blimp/net/blimp_connection_statistics.h

Index: blimp/net/blimp_connection_statistics.h
diff --git a/blimp/net/blimp_connection_statistics.h b/blimp/net/blimp_connection_statistics.h
new file mode 100644
index 0000000000000000000000000000000000000000..252d21c933bc760ed4f490a3eb34b683a6270d1d
--- /dev/null
+++ b/blimp/net/blimp_connection_statistics.h
@@ -0,0 +1,59 @@
+// Copyright 2016 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 BLIMP_NET_BLIMP_CONNECTION_STATISTICS_H_
+#define BLIMP_NET_BLIMP_CONNECTION_STATISTICS_H_
+
+#include <map>
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "blimp/net/blimp_net_export.h"
+
+namespace blimp {
+
+// Collects network traffic statistics. Maintains a counter for number of
+// completed commits, bytes sent and received over network and notifies its
+// observers on the main thread. Presents the data on a per navigation basis.
+// This class is supposed to live an entire session, created and destroyed along
+// it. This class internally takes care of the fact that the stats can be
+// written from multiple threads while it is read only from the UI thread.
+class BLIMP_NET_EXPORT BlimpConnectionStatistics {
+ public:
+  enum EventType {
+    BYTES_SENT = 0,
+    BYTES_RECEIVED = 1,
+    COMMIT = 2,
+  };
+  typedef std::map<EventType, int> StatisticsMap;
+
+  BlimpConnectionStatistics(
+      const scoped_refptr<base::TaskRunner>& main_thread_task_runner);
+
+  ~BlimpConnectionStatistics();
+
+  // Can be called from any thread.

[Kevin M, 2016/05/20 01:02:04]

Document the purpose and parameters of these functions

+  void Add(EventType type, int data);

[Kevin M, 2016/05/20 01:02:03]

We can use a better parameter name instead of "data", maybe "num"? "x"? lol

[shaktisahu, 2016/05/22 22:36:57]

I feel "data" is better than "x". 

+  void Increment(EventType type);
+
+  // Must be called only on UI thread.
+  void GetDebugInfo(const base::Callback<void(StatisticsMap stats)>& callback);

[Kevin M, 2016/05/20 01:02:04]

If we require that this method be invoked on the correct thread, then the values
are available for synchronous access, therefore there's no need for a callback.

We should probably just add an int Get(EventType type) method, which accesses a
value from the map.

[Kevin M, 2016/05/20 04:01:52]

After a bit of thought, I think we need to have the Add and Increment events
work on the UI thread, the reason being is that posting to the UI task runner
for every network event is hugely expensive.

[shaktisahu, 2016/05/22 22:36:57]

Thank you. This would be much better.

+
+ private:
+  StatisticsMap statistics_;
+
+  // Main thread counterparts of the stats collection functions.
+  void AddOnMain(EventType type, int data);
+  void IncrementOnMain(EventType type);
+
+  scoped_refptr<base::TaskRunner> main_thread_task_runner_;
+
+  base::WeakPtrFactory<BlimpConnectionStatistics> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(BlimpConnectionStatistics);
+};
+
+}  // namespace blimp
+
+#endif  // BLIMP_NET_BLIMP_CONNECTION_STATISTICS_H_