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

cc/memory_history.cc

+// Copyright 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.
+
+#include "cc/memory_history.h"
+
+namespace cc {
+
+// static
+scoped_ptr<MemoryHistory> MemoryHistory::create() {
+  return make_scoped_ptr(new MemoryHistory());
+}
+
+MemoryHistory::MemoryHistory() {
+}
+
+MemoryHistory::Entry MemoryHistory::GetEntry(const size_t& n) const {
+  DCHECK(n < ring_buffer_.BufferSize());
+
+  if (ring_buffer_.IsFilledIndex(n))
+    return ring_buffer_.ReadBuffer(n);
+
+  return MemoryHistory::Entry();
+}
+
+void MemoryHistory::SaveEntry(const MemoryHistory::Entry& entry) {
+  ring_buffer_.SaveToBuffer(entry);
+}
+
+void MemoryHistory::GetMinAndMax(size_t* min, size_t* max) const {
+  *min = std::numeric_limits<size_t>::max();
+  *max = 0;
+
+  for (size_t i = 0; i < ring_buffer_.BufferSize(); i++) {
+    if (!ring_buffer_.IsFilledIndex(i))
+        continue;
+    const Entry entry = ring_buffer_.ReadBuffer(i);
+    size_t bytes_total = entry.bytes_total();
+
+    if (bytes_total < *min)
+      *min = bytes_total;
+    if (bytes_total > *max)
+        *max = bytes_total;
+  }
+
+  if (*min > *max)
+    *min = *max;
+}
+
+}  // namespace cc