cc: Set sync token on resource even if context is lost.

cc/resources/resource_provider.cc

Index: cc/resources/resource_provider.cc
diff --git a/cc/resources/resource_provider.cc b/cc/resources/resource_provider.cc
index 49dae1d6ae988284713422c430f0f1e8a2f814e8..107b1f37acaf4f54eb8394a9ee87fc8ee0718c0f 100644
--- a/cc/resources/resource_provider.cc
+++ b/cc/resources/resource_provider.cc
@@ -1101,6 +1101,7 @@ ResourceProvider::ScopedWriteLockGL::ScopedWriteLockGL(
     bool create_mailbox)
     : resource_provider_(resource_provider),
       resource_id_(resource_id),
+      set_sync_token_(false),
       synchronized_(false) {
   DCHECK(thread_checker_.CalledOnValidThread());
   Resource* resource = resource_provider->LockForWrite(resource_id);
@@ -1123,8 +1124,10 @@ ResourceProvider::ScopedWriteLockGL::~ScopedWriteLockGL() {
   DCHECK(thread_checker_.CalledOnValidThread());
   Resource* resource = resource_provider_->GetResource(resource_id_);
   DCHECK(resource->locked_for_write);
-  if (sync_token_.HasData())
+  if (set_sync_token_) {

[danakj, 2016/10/05 01:44:05]

Explain this in a comment please. (Basically what you have in the CL
description.)

[sunnyps, 2016/10/06 02:45:06]

I removed the DCHECK here because the compositor context isn't necessarily lost
if the compositor and worker aren't in a share group.

+    DCHECK(sync_token_.HasData() || resource_provider_->IsGLContextLost());
     resource->UpdateSyncToken(sync_token_);
+  }
   if (synchronized_)
     resource->SetSynchronized();
   resource_provider_->UnlockForWrite(resource);