Unit tests have been created for the GPUTiming.

ui/gl/BUILD.gn

Index: ui/gl/BUILD.gn
diff --git a/ui/gl/BUILD.gn b/ui/gl/BUILD.gn
index 50abfc62b9d3250da760b5fd340a395cb6ffaf03..f5f4134290b6875a9d984b77e86bbb767885e007 100644
--- a/ui/gl/BUILD.gn
+++ b/ui/gl/BUILD.gn
@@ -268,6 +268,8 @@ source_set("gl_unittest_utils") {
     "gl_mock.cc",
     "gl_mock.h",
     "gl_mock_autogen_gl.h",
+    "gpu_timing_fake.cc",
+    "gpu_timing_fake.h",
   ]
 
   configs += [ "//third_party/khronos:khronos_headers" ]
@@ -281,6 +283,7 @@ source_set("gl_unittest_utils") {
 test("gl_unittests") {
   sources = [
     "gl_api_unittest.cc",
+    "gpu_timing_unittest.cc",
     "test/run_all_unittests.cc",
   ]
 
@@ -295,8 +298,10 @@ test("gl_unittests") {
 
   deps = [
     ":gl",
+    ":gl_unittest_utils",
     "//base",
     "//base/test:test_support",
+    "//testing/gmock",
     "//testing/gtest",
   ]
 }