Added methods to generate sync tokens for resource id(s).

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 3105feb6af7a7991ae426339715c3f03c01d6f85..98354a13d49633705455e3366bde13966217c703 100644
--- a/cc/resources/resource_provider.cc
+++ b/cc/resources/resource_provider.cc
@@ -753,6 +753,44 @@ void ResourceProvider::CopyToResource(ResourceId id,
   }
 }
 
+void ResourceProvider::GenerateSyncTokenForResource(ResourceId resource_id) {

[David Yen, 2016/02/17 21:53:28]

From piman@ (originally inside CopyToResource where I had inserted a fence sync
after every copy):

Most callers are debug/fallback paths and/or relatively rare calls (UI
resources), but one is the video path for software decode, where this would be
called 3 times per video frame (once for each plane). If there are concurrent
rasterization tasks, the ordering barriers can become (or cause) real flushes,
so that would be a regression I think.

Maybe we could make the caller responsible for doing the synchronization, and
provide a SynchronizeResources that could do a single fence/OB and set the token
on all resources?

[David Yen, 2016/02/17 21:54:36]

Done. There are probably other places CopyToResource() is used where this
function needs to be called, but I just added the 2 most obvious ones first.
Once I add in the DCHECK it will be more obvious where else we need to add sync
token generation.

+  Resource* resource = GetResource(resource_id);
+  if (!resource->needs_sync_token())
+    return;
+
+  gpu::SyncToken sync_token;
+  GLES2Interface* gl = ContextGL();
+  DCHECK(gl);
+
+  const uint64_t fence_sync = gl->InsertFenceSyncCHROMIUM();
+  gl->OrderingBarrierCHROMIUM();
+  gl->GenUnverifiedSyncTokenCHROMIUM(fence_sync, sync_token.GetData());
+
+  resource->UpdateSyncToken(sync_token);
+}
+
+void ResourceProvider::GenerateSyncTokenForResources(
+    const ResourceIdArray& resource_ids) {
+  gpu::SyncToken sync_token;
+  bool created_sync_token = false;
+  for (ResourceId id : resource_ids) {
+    Resource* resource = GetResource(id);
+    if (resource->needs_sync_token()) {
+      if (!created_sync_token) {
+        GLES2Interface* gl = ContextGL();
+        DCHECK(gl);
+
+        const uint64_t fence_sync = gl->InsertFenceSyncCHROMIUM();
+        gl->OrderingBarrierCHROMIUM();
+        gl->GenUnverifiedSyncTokenCHROMIUM(fence_sync, sync_token.GetData());
+        created_sync_token = true;
+      }
+
+      resource->UpdateSyncToken(sync_token);
+    }
+  }
+}
+
 ResourceProvider::Resource* ResourceProvider::InsertResource(
     ResourceId id,
     const Resource& resource) {