Relocate and refactor overview mode files.

ash/ash.gyp

Index: ash/ash.gyp
diff --git a/ash/ash.gyp b/ash/ash.gyp
index ab538980a5fdb4d9e2031098b6062008ca4eb17c..3ecaa9776da05551f47d55aa0d3942bbcbe6a294 100644
--- a/ash/ash.gyp
+++ b/ash/ash.gyp
@@ -430,6 +430,13 @@
         'wm/mru_window_tracker.h',
         'wm/overlay_event_filter.cc',
         'wm/overlay_event_filter.h',
+        'wm/overview/window_selector.cc',
+        'wm/overview/window_selector.h',
+        'wm/overview/window_selector_controller.cc',
+        'wm/overview/window_selector_controller.h',
+        'wm/overview/window_selector_delegate.h',
+        'wm/overview/window_selector_window.cc',
+        'wm/overview/window_selector_window.h',
         'wm/panels/panel_frame_view.cc',
         'wm/panels/panel_frame_view.h',
         'wm/panels/panel_layout_manager.cc',
@@ -488,11 +495,6 @@
         'wm/window_properties.h',
         'wm/window_resizer.cc',
         'wm/window_resizer.h',
-        'wm/window_selector.cc',
-        'wm/window_selector.h',
-        'wm/window_selector_controller.cc',
-        'wm/window_selector_controller.h',
-        'wm/window_selector_delegate.h',
         'wm/window_util.cc',
         'wm/window_util.h',
         'wm/workspace_controller.cc',
@@ -745,6 +747,7 @@
         'wm/drag_window_resizer_unittest.cc',
         'wm/frame_painter_unittest.cc',
         'wm/lock_state_controller_impl2_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',
@@ -761,7 +764,6 @@
         'wm/window_cycle_controller_unittest.cc',
         'wm/window_manager_unittest.cc',
         'wm/window_modality_controller_unittest.cc',
-        'wm/window_selector_unittest.cc',
         'wm/window_util_unittest.cc',
         'wm/workspace_controller_test_helper.cc',
         'wm/workspace_controller_test_helper.h',