Remove ContextProvider::IsContextLost.

ui/compositor/test/in_process_context_provider.cc

Index: ui/compositor/test/in_process_context_provider.cc
diff --git a/ui/compositor/test/in_process_context_provider.cc b/ui/compositor/test/in_process_context_provider.cc
index 4885c60d4311e2d2e5322b5e4fcabee662e0ca33..a29bb9d27edba4d7ef1f86a27d6a8c8a3c9356a2 100644
--- a/ui/compositor/test/in_process_context_provider.cc
+++ b/ui/compositor/test/in_process_context_provider.cc
@@ -189,13 +189,6 @@ base::Lock* InProcessContextProvider::GetLock() {
   return &context_lock_;
 }
 
-bool InProcessContextProvider::IsContextLost() {
-  DCHECK(context_thread_checker_.CalledOnValidThread());
-
-  base::AutoLock lock(destroyed_lock_);
-  return destroyed_;
-}
-
 void InProcessContextProvider::VerifyContexts() {
 }