Add LowMemoryNotification to the API on Android platform.

Add LowMemoryNotification to the API on Android platform.

Android system provides a unique feature that it sends a notification to the
browser in low memory condition, and the browser cleans up cache and frees
resources. Forcing a GC in low memory condition can free DOM objects and also
can shrink the old spaces.

This patch addresses the last comment in
http://codereview.chromium.org/173016/show

Mads Ager 2009/08/19 17:24:23
I would prefer to not use the flags to signal that a compacting collection is
requested.

TBR = ager
Review URL: http://codereview.chromium.org/173102

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2725 ce2b1a6d-e550-0410-aec6-3dcde31c8c00