Suppress a benign/false-positive race in ThreadCollisionWarner and a benign race in CookieMonster Histogram handling
Suppress a benign/false-positive race in ThreadCollisionWarner and a benign race in CookieMonster Histogram handling

For the first race, the reports look like this:
WARNING: Possible data race during write of size 4 at 0080F90C: {{{
   T26 (L{}):
    #0  base::subtle::NoBarrier_Store base/atomicops_internals_x86_msvc.h:67
    #1  base::ThreadCollisionWarner::Leave base/thread_collision_warner.cc:60
           ...
  Concurrent write(s) happened at (OR AFTER) these points:
   T27 (L{}):
    #0  base::subtle::NoBarrier_Store base/atomicops_internals_x86_msvc.h:66
    #1  base::ThreadCollisionWarner::Leave base/thread_collision_warner.cc:60

And the code is:
void ThreadCollisionWarner::Leave() {
  if (subtle::Barrier_AtomicIncrement(&counter_, -1) == 0) {
    subtle::NoBarrier_Store(&valid_thread_id_, 0);
  }
}

TBR=glider
BUG=62694
Review URL: http://codereview.chromium.org/4837004

git-svn-id: http://src.chromium.org/svn/trunk/src@65941 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: e48cdf624a69059729c8f5b164c04139fe6c6485
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser