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

chrome/browser/net/sdch_dictionary_fetcher.cc

Index: chrome/browser/net/sdch_dictionary_fetcher.cc
diff --git a/chrome/browser/net/sdch_dictionary_fetcher.cc b/chrome/browser/net/sdch_dictionary_fetcher.cc
index 4a96f8fff37087d207aeb35681215342861b2e5e..24bdf9337fa2065838738272373912d69e514662 100644
--- a/chrome/browser/net/sdch_dictionary_fetcher.cc
+++ b/chrome/browser/net/sdch_dictionary_fetcher.cc
@@ -14,9 +14,11 @@
 SdchDictionaryFetcher::SdchDictionaryFetcher()
     : ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)),
       task_is_pending_(false) {
+  DCHECK(CalledOnValidThread());
 }
 
 SdchDictionaryFetcher::~SdchDictionaryFetcher() {
+  DCHECK(CalledOnValidThread());
 }
 
 // static
@@ -25,6 +27,8 @@ void SdchDictionaryFetcher::Shutdown() {
 }
 
 void SdchDictionaryFetcher::Schedule(const GURL& dictionary_url) {
+  DCHECK(CalledOnValidThread());
+
   // Avoid pushing duplicate copy onto queue.  We may fetch this url again later
   // and get a different dictionary, but there is no reason to have it in the
   // queue twice at one time.