Implement MD simple gesture nav

ui/vector_icons/BUILD.gn

 # 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("//ui/vector_icons/vector_icons.gni")
 
 aggregate_vector_icons("ui_vector_icons") {
   icon_directory = "."
 
   icons = [
     "close.1x.icon",
     "close.icon",
+    "back_arrow.1x.icon",

[Evan Stade, 2017/02/08 16:08:10]

nit: alphabetize

[mohsen, 2017/02/08 20:52:03]

Oops! Done.

+    "back_arrow.icon",
+    "forward_arrow.1x.icon",
+    "forward_arrow.icon",
   ]
 }
 
 static_library("vector_icons") {
   sources = get_target_outputs(":ui_vector_icons")
   sources += [ "//ui/gfx/vector_icon_types.h" ]
 
   deps = [
     ":ui_vector_icons",
     "//base",
     "//skia",
   ]
 }