Render the tab close button as a vector-based icon.

ui/gfx/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 448 matching lines @@
     "vector_icons/sad_tab.icon",
     "vector_icons/smartphone.icon",
     "vector_icons/star.icon",
     "vector_icons/star_border.icon",
     "vector_icons/supervisor_account.icon",
     "vector_icons/tab.icon",
     "vector_icons/tab_audio.1x.icon",
     "vector_icons/tab_audio.icon",
     "vector_icons/tab_audio_muting.1x.icon",
     "vector_icons/tab_audio_muting.icon",
+    "vector_icons/tab_close_hovered_pressed.1x.icon",
+    "vector_icons/tab_close_hovered_pressed.icon",
+    "vector_icons/tab_close_normal.1x.icon",
+    "vector_icons/tab_close_normal.icon",
     "vector_icons/tablet.icon",
     "vector_icons/translate.icon",
     "vector_icons/warning.icon",
     "vector_icons/warning_badge.icon",
     "vector_icons/web.icon",
   ]
   outputs = [
     vector_icons_cc_file,
     vector_icons_h_file,
   ]
@@ skipping 203 matching lines @@
 if (is_android) {
   generate_jni("gfx_jni_headers") {
     sources = [
       "../android/java/src/org/chromium/ui/gfx/BitmapHelper.java",
       "../android/java/src/org/chromium/ui/gfx/DeviceDisplayInfo.java",
       "../android/java/src/org/chromium/ui/gfx/ViewConfigurationHelper.java",
     ]
     jni_package = "gfx"
   }
 }