Add a buildflag to use the handle verifier in a per module mode.

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index 5712663ed8bc334414a91a68cdc0ea64eb9ce422..76403af8ab7b5fc0967a9cfb05ae5c48d83c0e60 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -1179,6 +1179,8 @@ component("base") {
 
     deps += [ "//base/trace_event/etw_manifest:chrome_events_win" ]
 
+    public_deps += [ "//base/win:base_win_features" ]

[Nico, 2016/06/03 14:41:16]

it looks like the new feature define is only used in a cc file and its test. if
you add this to public_deps, then every file in every target depending on base
(almost all of them) will get a new -D flag, while it's really only needed in
two files. Maybe this should just be an ordinary dep in base and base_unittests?

[Sébastien Marchand, 2016/06/03 14:44:42]

Oh, I thought that we were strongly encouraged to always use the new buildflag
definition for any new build flag. I agree that in this case it make more sense
to just add the define for these 2 targets, I'll do this.

+
     if (is_component_build) {
       # Copy the VS runtime DLLs into the isolate so that they don't have to be
       # preinstalled on the target machine. The debug runtimes have a "d" at