Trace amount of external memory with --trace-gc-verbose.

R=hpayer@google.com

Review URL: https://codereview.chromium.org/16953002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15108 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
build fix for 15107

R=svenpanne@chromium.org
BUG=

Review URL: https://codereview.chromium.org/16954004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15109 ce2b1a6d-e550-0410-aec6-3dcde31c8c00