Introducing gpu::CommandBufferId as a distinct, IdType<...>-based type.

gpu/command_buffer/common/id_type_unittest.cc

Index: gpu/command_buffer/common/id_type_unittest.cc
diff --git a/content/common/id_type_unittest.cc b/gpu/command_buffer/common/id_type_unittest.cc
similarity index 98%
rename from content/common/id_type_unittest.cc
rename to gpu/command_buffer/common/id_type_unittest.cc
index de221cf1669a8ca3e5c8c0fdd057a20923d6696d..cfc70f10f5c9aee8b05bd509cf59d18e2cb15348 100644
--- a/content/common/id_type_unittest.cc
+++ b/gpu/command_buffer/common/id_type_unittest.cc
@@ -9,10 +9,10 @@
 #include <type_traits>
 #include <unordered_map>
 
-#include "content/common/id_type.h"
+#include "gpu/command_buffer/common/id_type.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-namespace content {
+namespace gpu {
 
 namespace {
 
@@ -197,4 +197,4 @@ INSTANTIATE_TEST_CASE_P(,
                                           123,
                                           std::numeric_limits<int>::max()));
 
-}  // namespace content
+}  // namespace base