Add GCTracer metrics for a scavenger GC for DOM wrappers

Add GCTracer metrics for a scavenger GC for DOM wrappers

This patch adds the following three metrics for the --trace_gc_nvp option.

nodes_died_in_new_space_; // Number of died nodes in the new space.
nodes_copied_in_new_space_; // Number of copied nodes to the new space.
nodes_promoted; // Number of promoted nodes to the old space.

BUG=
TEST=Manually confirmed that the "--trace_gc --trace_gc_nvp" option prints the metrics

Review URL: https://codereview.chromium.org/11365146
Patch from Kentaro Hara <haraken@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13159 ce2b1a6d-e550-0410-aec6-3dcde31c8c00