Replace usage of SurfaceId's client_id with FrameSinkId

cc/trees/surface_sequence_generator.cc

Index: cc/trees/surface_sequence_generator.cc
diff --git a/cc/trees/surface_sequence_generator.cc b/cc/trees/surface_sequence_generator.cc
index f2196892519bbe57661b6c78fed8570fcd2d8215..83e9a62fa1b75d395c08e1f612b9e0aac198be4b 100644
--- a/cc/trees/surface_sequence_generator.cc
+++ b/cc/trees/surface_sequence_generator.cc
@@ -8,12 +8,12 @@
 namespace cc {
 
 SurfaceSequenceGenerator::SurfaceSequenceGenerator()
-    : surface_client_id_(0u), next_surface_sequence_(1u) {}
+    : next_surface_sequence_(1u) {}
 
 SurfaceSequenceGenerator::~SurfaceSequenceGenerator() = default;
 
 SurfaceSequence SurfaceSequenceGenerator::CreateSurfaceSequence() {
-  return SurfaceSequence(surface_client_id_, next_surface_sequence_++);
+  return SurfaceSequence(frame_sink_id_, next_surface_sequence_++);
 }
 
 }  // namespace cc