Splitting up RenderWidgetHostLatencyTracker and some renames.

ui/latency/BUILD.gn

-# Copyright 2014 The Chromium Authors. All rights reserved.
+# Copyright 2017 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("//testing/test.gni")
 
 source_set("latency") {
   sources = [
+    "latency/latency_histogram_macros.h",
     "latency_info.cc",
     "latency_info.h",
+    "latency_tracker.cc",
+    "latency_tracker.h",
   ]
 
   deps = [
     "//base",
     "//ui/gfx",
   ]
 }
 
 test("latency_unittests") {
   sources = [
@@ skipping 15 matching lines @@
       "mojo/struct_traits_unittest.cc",
     ]
     deps += [
       "//ipc:test_support",
       "//mojo/public/cpp/bindings",
       "//ui/latency/ipc",
       "//ui/latency/mojo:test_interfaces",
     ]
   }
 }