Earlier quoted context omitted.
Indeed, "free memory" is the biggest waste of money and energy imaginable. Unless you lack the memory necessary to do something else, you shouldn't care. If the question really needs answering, the poster should just get a heap profile. Some instructions are here: http://goog-perftools.sourceforge.net/doc/heap_profiler.html You may also wish to try the memlog flag to chrome, or rebuild chrome with TCMALLOC_SMALL_BUT_…
Unless you lack the memory necessary to do something else, you shouldn't care. This is exactly the attitude that leads to such problems. Applications that assume they can use all of the available memory on the machine are hostile to multitasking environments.
Entirely unused RAM is a waste if never used.