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

chrome/browser/renderer_host/backing_store_x.cc

Index: chrome/browser/renderer_host/backing_store_x.cc
diff --git a/chrome/browser/renderer_host/backing_store_x.cc b/chrome/browser/renderer_host/backing_store_x.cc
index a2397a2dd3857465a3b85a3dc1eae40377987616..eb7663633f35accc6c5a1be77a98be573ad5f6b5 100644
--- a/chrome/browser/renderer_host/backing_store_x.cc
+++ b/chrome/browser/renderer_host/backing_store_x.cc
@@ -77,6 +77,13 @@ BackingStore::~BackingStore() {
   XFreeGC(display_, static_cast<GC>(pixmap_gc_));
 }
 
+size_t BackingStore::MemorySize() {
+  if (use_render_)

[agl, 2009/06/24 18:53:01]

!use_render_

+    return size_.GetArea() * (pixmap_bpp_ / 8);
+  else
+    return size_.GetArea() * 4;  // TODO(port) is this correct?

[agl, 2009/06/24 18:53:01]

Yes it is, remove TODO

+}
+
 void BackingStore::PaintRectWithoutXrender(TransportDIB* bitmap,
                                            const gfx::Rect &bitmap_rect) {
   const int width = bitmap_rect.width();