[cc] Show GPU memory usage and overage below FPS counter

cc/memory_history.h

+// Copyright 2013 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 CC_MEMORY_HISTORY_H_
+#define CC_MEMORY_HISTORY_H_
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/time.h"
+#include "cc/ring_buffer.h"
+
+namespace cc {
+
+// Maintains a history of memory for each frame
+class MemoryHistory {
+ public:
+  static scoped_ptr<MemoryHistory> create();
+
+  size_t HistorySize() const { return ring_buffer_.BufferSize(); }
+
+  struct Entry {
+  Entry()
+      : bytes_allocated(0),
+        bytes_over(0) { }
+
+      size_t bytes_allocated;
+      size_t bytes_unreleasable;
+      size_t bytes_over;
+      size_t bytes_total() const {
+          return bytes_allocated +
+              bytes_unreleasable +
+              bytes_over;
+      }
+  };
+
+  // n = 0 returns the oldest and
+  // n = HistorySize() - 1 the most recent paint time.
+  Entry GetEntry(const size_t& n) const;
+
+  void SaveEntry(const Entry& entry);
+  void GetMinAndMax(size_t* min, size_t* max) const;
+
+ private:
+  MemoryHistory();
+
+  RingBuffer<Entry, 80> ring_buffer_;
+
+  DISALLOW_COPY_AND_ASSIGN(MemoryHistory);
+};
+
+}  // namespace cc
+
+#endif  // CC_MEMORY_HISTORY_H_