[Sync] Clear LocalDeviceInfoProvider cache on sync DB destruction.

components/sync_driver/local_device_info_provider_impl.h

Index: components/sync_driver/local_device_info_provider_impl.h
diff --git a/components/sync_driver/local_device_info_provider_impl.h b/components/sync_driver/local_device_info_provider_impl.h
index 29dc715228add1d0c8db55c0d91854365ebb523c..07ba2d720e0d653b04ebb5a696ce8ff6aecd2397 100644
--- a/components/sync_driver/local_device_info_provider_impl.h
+++ b/components/sync_driver/local_device_info_provider_impl.h
@@ -7,6 +7,7 @@
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "base/threading/non_thread_safe.h"
 #include "components/sync_driver/device_info.h"
 #include "components/sync_driver/local_device_info_provider.h"
 #include "components/version_info/version_info.h"
@@ -14,7 +15,8 @@
 namespace browser_sync {
 
 class LocalDeviceInfoProviderImpl
-    : public sync_driver::LocalDeviceInfoProvider {
+    : public sync_driver::LocalDeviceInfoProvider,
+      public base::NonThreadSafe {
  public:
   LocalDeviceInfoProviderImpl(version_info::Channel channel,
                               const std::string& version,
@@ -31,6 +33,7 @@ class LocalDeviceInfoProviderImpl
       const scoped_refptr<base::TaskRunner>& blocking_task_runner) override;
   std::unique_ptr<Subscription> RegisterOnInitializedCallback(
       const base::Closure& callback) override;
+  void Clear() override;
 
  private:
   void InitializeContinuation(const std::string& guid,