Update from https://crrev.com/316786

mojo/cc/context_provider_mojo.cc

Index: mojo/cc/context_provider_mojo.cc
diff --git a/mojo/cc/context_provider_mojo.cc b/mojo/cc/context_provider_mojo.cc
index 9d57e52c8d1ce3f5bbd8933187c1ecca19ad91e5..3a32a5ef1a2b0a6a80850a491eb3e501e214424d 100644
--- a/mojo/cc/context_provider_mojo.cc
+++ b/mojo/cc/context_provider_mojo.cc
@@ -46,6 +46,13 @@ cc::ContextProvider::Capabilities ContextProviderMojo::ContextCapabilities() {
   return capabilities_;
 }
 
+void ContextProviderMojo::SetupLock() {
+}
+
+base::Lock* ContextProviderMojo::GetLock() {
+  return &context_lock_;
+}
+
 bool ContextProviderMojo::IsContextLost() {
   return context_lost_;
 }