Make SDCH classes IO-thread-only. Remove TSan suppression.

chrome/browser/browser_process_impl.cc

Index: chrome/browser/browser_process_impl.cc
diff --git a/chrome/browser/browser_process_impl.cc b/chrome/browser/browser_process_impl.cc
index e84a21998b52dfe97c89f9785d920a5a83869cef..d95941e52bb41fb0b754d5b2e8bb0a4a0912c8ab 100644
--- a/chrome/browser/browser_process_impl.cc
+++ b/chrome/browser/browser_process_impl.cc
@@ -184,7 +184,8 @@ void BrowserProcessImpl::StartTearDown() {
   // a pointer to a URLFetcher, and that URLFetcher (upon destruction) will do
   // a PostDelayedTask onto the IO thread.  This shutdown call will both discard
   // any pending URLFetchers, and avoid creating any more.
-  SdchDictionaryFetcher::Shutdown();
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+                          base::Bind(&SdchDictionaryFetcher::Shutdown));
 
   // We need to destroy the MetricsService, GoogleURLTracker,
   // IntranetRedirectDetector, and SafeBrowsing ClientSideDetectionService