Suppress reports on benign race on vfptr in ChromeThread.
Suppress reports on benign race on vfptr in ChromeThread.

This has started showing up on TSan/Linux/unit like this:
WARNING: Possible data race during write of size 4 at 0xAEF33E0: {{{
   T0 (locks held: {}):
    #0  ChromeThread::~ChromeThread() chrome/browser/chrome_thread.cc:44
    #1  ImageLoadingTrackerTest::~ImageLoadingTrackerTest() chrome/browser/extensions/image_loading_tracker_unittest.cc:17
    #2  ImageLoadingTrackerTest_Cache_Test::~ImageLoadingTrackerTest_Cache_Test() chrome/browser/extensions/image_loading_tracker_unittest.cc:95
    #3  testing::internal::TestInfoImpl::Run() testing/gtest/src/gtest.cc:2319
  Concurrent read(s) happened at (OR AFTER) these points:
   T462 (Chrome_IOThread) (locks held: {}):
    #0  base::Thread::ThreadMain() base/thread.cc:156
    #1  ThreadFunc(void*) base/platform_thread_posix.cc:26
    #2  ThreadSanitizerStartThread ts_valgrind_intercepts.c:571
}}}

http://build.chromium.org/buildbot/memory/builders/Linux%20Tests%20(tsan)/builds/3340

TBR=glider
BUG=25385
Review URL: http://codereview.chromium.org/1572008

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@43189 0039d316-1c4b-4281-b951-d872f2087c98

gavinp/chromium,ropik/chromium,gavinp/chromium,gavinp/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,gavinp/chromium,adobe/chromium,yitian134/chromium,gavinp/chromium,adobe/chromium,adobe/chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,yitian134/chromium,ropik/chromium,ropik/chromium,adobe/chromium,yitian134/chromium,adobe/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,ropik/chromium,gavinp/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,adobe/chromium,adobe/chromium,adobe/chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,adobe/chromium