Re-enable Dr. Memory's -callstack_use_top_fp_selectively option for Chrome, given recent fixes in callstack walking.

BUG=https://code.google.com/p/drmemory/issues/detail?id=851
TBR=zhaoqin@chromium.org

Review URL: https://codereview.chromium.org/178143002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252932 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252932