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

cc/surfaces/surface_id_allocator.cc

Index: cc/surfaces/surface_id_allocator.cc
diff --git a/cc/surfaces/surface_id_allocator.cc b/cc/surfaces/surface_id_allocator.cc
index 330b3c3247299f95da6ef235c112e8759469adc9..a3bc70da667654bc28dec1f385de17bf768300e1 100644
--- a/cc/surfaces/surface_id_allocator.cc
+++ b/cc/surfaces/surface_id_allocator.cc
@@ -6,8 +6,6 @@
 
 #include <stdint.h>
 
-#include "base/rand_util.h"
-
 namespace cc {
 
 SurfaceIdAllocator::SurfaceIdAllocator(uint32_t client_id)
@@ -17,8 +15,7 @@ SurfaceIdAllocator::~SurfaceIdAllocator() {
 }
 
 SurfaceId SurfaceIdAllocator::GenerateId() {
-  uint64_t nonce = base::RandUint64();
-  SurfaceId id(client_id_, next_id_, nonce);
+  SurfaceId id(client_id_, next_id_);
   next_id_++;
   return id;
 }