Replaced cc::SurfaceId::nonce_ with base::UnguessableToken

cc/surfaces/surface_manager.cc

Index: cc/surfaces/surface_manager.cc
diff --git a/cc/surfaces/surface_manager.cc b/cc/surfaces/surface_manager.cc
index b0b814fb1b2d212e841bc4b4a10f724d6b4aade8..b8b121142ff7f18f707f9dea142be0f0faa6c6ee 100644
--- a/cc/surfaces/surface_manager.cc
+++ b/cc/surfaces/surface_manager.cc
@@ -16,9 +16,6 @@
 
 namespace cc {
 
-const SurfaceId SurfaceManager::kRootSurfaceId(FrameSinkId(0u, 0u),
-                                               LocalFrameId(0u, 0u));
-
 SurfaceManager::FrameSinkSourceMapping::FrameSinkSourceMapping()
     : client(nullptr), source(nullptr) {}
 
@@ -30,7 +27,9 @@ SurfaceManager::FrameSinkSourceMapping::~FrameSinkSourceMapping() {
                      << ", children: " << children.size();
 }
 
-SurfaceManager::SurfaceManager() {
+SurfaceManager::SurfaceManager()
+    : kRootSurfaceId(FrameSinkId(0u, 0u),
+                     LocalFrameId(0u, base::UnguessableToken::Create())) {
   thread_checker_.DetachFromThread();
 }