Split the event library into a cross-platform and native part. Part 1.

ui/events/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")
 
 static_library("dom4_keycode_converter") {
   sources = [
     "keycodes/dom4/keycode_converter.cc",
     "keycodes/dom4/keycode_converter.h",
@@ skipping 41 matching lines @@
   defines = [ "EVENTS_BASE_IMPLEMENTATION" ]
 
   deps = [
     ":dom4_keycode_converter",
     "//base/third_party/dynamic_annotations",
     "//skia",
   ]
 
   public_deps = [
     "//base",
-    "//ui/events/platform",
     "//ui/gfx",
     "//ui/gfx/geometry",
   ]
 
   if (use_x11) {
     configs += [ "//build/config/linux:x11" ]
 
     sources += [
       "keycodes/keyboard_code_conversion_x.cc",
       "keycodes/keyboard_code_conversion_x.h",
@@ skipping 187 matching lines @@
     "gesture_detection/gesture_provider_unittest.cc",
     "gesture_detection/motion_event_buffer_unittest.cc",
     "gesture_detection/motion_event_generic_unittest.cc",
     "gesture_detection/touch_disposition_gesture_filter_unittest.cc",
     "gesture_detection/velocity_tracker_unittest.cc",
     "gestures/fling_curve_unittest.cc",
     "gestures/gesture_provider_impl_unittest.cc",
     "keycodes/dom4/keycode_converter_unittest.cc",
     "latency_info_unittest.cc",
     "platform/platform_event_source_unittest.cc",
+    "platform/platform_event_builder_x_unittest.cc",
     "x/events_x_unittest.cc",
   ]
 
   deps = [
     ":dom4_keycode_converter",
     ":events",
     ":events_base",
     ":gesture_detection",
     ":test_support",
     "//base",
     "//base/test:run_all_unittests",
     "//skia",
     "//testing/gtest",
     "//ui/events/platform",
     "//ui/gfx:test_support",
   ]
 
   if (use_x11) {
     configs += [ "//build/config/linux:x11" ]
     deps += [ "//ui/gfx/x" ]
   } else {
-    sources -= [ "x/events_x_unittest.cc" ]
+    sources -= [
+      "platform/platform_event_builder_x_unittest.cc",
+      "x/events_x_unittest.cc",
+    ]
   }
 }