chrome/browser/android/compositor/tab_content_manager.h has some maps in it for LayerMap and ThumbnailLayerMap.

These sound like they might be small. Currently they're unordered_maps which will be wasting a lot of space for hash tables. I'm changing them to std::map.

But I can't check how big these actually are. If they are small, we should be using a base::flat_map instead.