change backing store cache to be memory-based rather than count

chrome/browser/renderer_host/backing_store_win.cc

 // Copyright (c) 2006-2008 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 "chrome/browser/renderer_host/backing_store.h"
 
 #include "base/command_line.h"
 #include "base/gfx/gdi_util.h"
 #include "chrome/browser/renderer_host/render_widget_host.h"
 #include "chrome/common/chrome_switches.h"
@@ skipping 56 matching lines @@
   if (original_bitmap_) {
     SelectObject(hdc_, original_bitmap_);
   }
   if (backing_store_dib_) {
     DeleteObject(backing_store_dib_);
     backing_store_dib_ = NULL;
   }
   DeleteDC(hdc_);
 }
 
+size_t BackingStore::MemorySize() {
+  return size_.GetArea() * (color_depth_ / 8);
+}
+
 // static
 bool BackingStore::ColorManagementEnabled() {
   static bool enabled = false;
   static bool checked = false;
   if (!checked) {
     checked = true;
     const CommandLine& command = *CommandLine::ForCurrentProcess();
     enabled = command.HasSwitch(switches::kEnableMonitorProfile);
   }
   return enabled;
@@ skipping 39 matching lines @@
   ScrollDC(hdc_, dx, dy, NULL, &r, NULL, &damaged_rect);
 
   // TODO(darin): this doesn't work if dx and dy are both non-zero!
   DCHECK(dx == 0 || dy == 0);
 
   // We expect that damaged_rect should equal bitmap_rect.
   DCHECK(gfx::Rect(damaged_rect) == bitmap_rect);
 
   PaintRect(process, bitmap, bitmap_rect);
 }