Remove knowledge of Chrome-specific SyncableService classes from WebDataService.

base/supports_user_data.cc

Index: base/supports_user_data.cc
diff --git a/base/supports_user_data.cc b/base/supports_user_data.cc
index 2a0263ed0d1881e6552f04b44a34fadf3e441cb2..a75e5192aa9d25c10ad7ffd2da0925cbd975e3b8 100644
--- a/base/supports_user_data.cc
+++ b/base/supports_user_data.cc
@@ -11,6 +11,10 @@ SupportsUserData::SupportsUserData() {
   thread_checker_.DetachFromThread();
 }
 
+SupportsUserData::~SupportsUserData() {
+  DCHECK(thread_checker_.CalledOnValidThread() || user_data_.empty());
+}
+
 SupportsUserData::Data* SupportsUserData::GetUserData(const void* key) const {
   DCHECK(thread_checker_.CalledOnValidThread());
   DataMap::const_iterator found = user_data_.find(key);
@@ -33,8 +37,4 @@ void SupportsUserData::DetachUserDataThread() {
   thread_checker_.DetachFromThread();
 }
 
-SupportsUserData::~SupportsUserData() {
-  DCHECK(thread_checker_.CalledOnValidThread() || user_data_.empty());
-}
-
 }  // namespace base