Support longpress drag selection

ui/touch_selection/ui_touch_selection.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
       'target_name': 'ui_touch_selection',
       'type': '<(component)',
       'dependencies': [
         '../../base/base.gyp:base',
         '../base/ui_base.gyp:ui_base',
         '../events/events.gyp:events',
         '../events/events.gyp:gesture_detection',
         '../gfx/gfx.gyp:gfx_geometry',
       ],
       'defines': [
         'UI_TOUCH_SELECTION_IMPLEMENTATION',
       ],
       'sources': [
+        'longpress_drag_selector.cc',
+        'longpress_drag_selector.h',
         'selection_event_type.h',
         'touch_handle.cc',
         'touch_handle.h',
         'touch_handle_orientation.h',
         'touch_selection_controller.cc',
         'touch_selection_controller.h',
+        'touch_selection_draggable.h',
         'ui_touch_selection_export.h',
       ],
       'include_dirs': [
         '../..',
       ],
     },
     {
       'target_name': 'ui_touch_selection_unittests',
       'type': '<(gtest_target_type)',
       'dependencies': [
@@ skipping 75 matching lines @@
               'dependencies': [
                 '../../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
               ],
             }],
           ],
         },
       ],
     }],
   ],
 }