Unit tests have been created for the GPUTiming.

ui/gl/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")
   import("//build/config/android/rules.gni")
@@ skipping 250 matching lines @@
 }
 
 source_set("gl_unittest_utils") {
   testonly = true
   sources = [
     "gl_bindings_autogen_mock.cc",
     "gl_bindings_autogen_mock.h",
     "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" ]
 
   deps = [
     ":gl",
     "//testing/gmock",
   ]
 }
 
 test("gl_unittests") {
   sources = [
     "gl_api_unittest.cc",
+    "gpu_timing_unittest.cc",
     "test/run_all_unittests.cc",
   ]
 
   deps = [
     ":gl",
+    ":gl_unittest_utils",
     "//base",
     "//base/test:test_support",
+    "//testing/gmock",
     "//testing/gtest",
   ]
 }
 
 if (is_android) {
   generate_jar_jni("surface_jni_headers") {
     jni_package = "ui/gl"
     classes = [ "android/view/Surface.class" ]
   }
 
   generate_jni("gl_jni_headers") {
     deps = [
       ":surface_jni_headers",
     ]
     sources = [
       "../android/java/src/org/chromium/ui/gl/SurfaceTextureListener.java",
       "../android/java/src/org/chromium/ui/gl/SurfaceTexturePlatformWrapper.java",
     ]
     jni_package = "ui/gl"
   }
 }