Remove "solo window" feature

ash/ash.gyp

 # Copyright (c) 2012 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,
     'grit_out_dir': '<(SHARED_INTERMEDIATE_DIR)/chrome',
   },
   'includes': [
@@ skipping 522 matching lines @@
         'wm/resize_shadow.cc',
         'wm/resize_shadow.h',
         'wm/resize_shadow_controller.cc',
         'wm/resize_shadow_controller.h',
         'wm/root_window_layout_manager.cc',
         'wm/root_window_layout_manager.h',
         'wm/screen_dimmer.cc',
         'wm/screen_dimmer.h',
         'wm/session_state_animator.cc',
         'wm/session_state_animator.h',
-        'wm/solo_window_tracker.cc',
-        'wm/solo_window_tracker.h',
         'wm/stacking_controller.cc',
         'wm/stacking_controller.h',
         'wm/status_area_layout_manager.cc',
         'wm/status_area_layout_manager.h',
         'wm/system_background_controller.cc',
         'wm/system_background_controller.h',
         'wm/system_gesture_event_filter.cc',
         'wm/system_gesture_event_filter.h',
         'wm/system_modal_container_event_filter.cc',
         'wm/system_modal_container_event_filter.h',
@@ skipping 297 matching lines @@
         'wm/header_painter_unittest.cc',
         'wm/immersive_fullscreen_controller_unittest.cc',
         'wm/lock_state_controller_unittest.cc',
         'wm/mru_window_tracker_unittest.cc',
         'wm/overview/window_selector_unittest.cc',
         'wm/panels/panel_layout_manager_unittest.cc',
         'wm/panels/panel_window_resizer_unittest.cc',
         'wm/partial_screenshot_view_unittest.cc',
         'wm/resize_shadow_and_cursor_unittest.cc',
         'wm/screen_dimmer_unittest.cc',
-        'wm/solo_window_tracker_unittest.cc',
         'wm/stacking_controller_unittest.cc',
         'wm/system_gesture_event_filter_unittest.cc',
         'wm/system_modal_container_layout_manager_unittest.cc',
         'wm/toplevel_window_event_handler_unittest.cc',
         'wm/user_activity_detector_unittest.cc',
         'wm/video_detector_unittest.cc',
         'wm/window_animations_unittest.cc',
         'wm/window_cycle_controller_unittest.cc',
         'wm/window_manager_unittest.cc',
         'wm/window_modality_controller_unittest.cc',
@@ skipping 137 matching lines @@
             },
           },
           'dependencies': [
             '../sandbox/sandbox.gyp:sandbox',
           ],
         }],
       ],
     },
   ],
 }