[ash-md] Prevents auto-positioning after cancelling overview

ash/common/wm/overview/window_selector.cc

Index: ash/common/wm/overview/window_selector.cc
diff --git a/ash/common/wm/overview/window_selector.cc b/ash/common/wm/overview/window_selector.cc
index b24142b14492ce3febf825e12b5aea27378d7c57..db099179f44f11be6de5ad79f671de3fec268350 100644
--- a/ash/common/wm/overview/window_selector.cc
+++ b/ash/common/wm/overview/window_selector.cc
@@ -381,6 +381,10 @@ void WindowSelector::Init(const WindowList& windows) {
 // may cause other, unrelated classes, (ie PanelLayoutManager) to make indirect
 // calls to restoring_minimized_windows() on a partially destructed object.
 void WindowSelector::Shutdown() {
+  // Stop observing screen metrics changes first to avoid auto-positioning
+  // windows in response to work area changes from window activation.
+  display::Screen::GetScreen()->RemoveObserver(this);
+
   size_t remaining_items = 0;
   for (std::unique_ptr<WindowGrid>& window_grid : grid_list_) {
     for (WindowSelectorItem* window_selector_item : window_grid->window_list())
@@ -553,12 +557,8 @@ void WindowSelector::OnDisplayRemoved(const display::Display& display) {
 
 void WindowSelector::OnDisplayMetricsChanged(const display::Display& display,
                                              uint32_t metrics) {
-  // If only the work area changes, there is no need to reposition windows in
-  // overview.
-  if (metrics != DISPLAY_METRIC_WORK_AREA) {

[oshima, 2016/08/09 10:59:56]

Note that we used to ignore work area only metrics change and this was to keep
the same behavior. Are you sure it's safer?

[varkha, 2016/08/09 13:13:39]

Yes, this callback is here to position windows and UI elements while in overview
mode when work area changes. Work area insets such as from the shelf, ChromeVox,
etc. should trigger repositioning. While we attempt to block those insets from
changing in overview I think it is safer to still respond to those changes while
still in overview.
So for instance, if there is some shortcut to activate ChromeVox while in
overview, the new code will deal with it while the old code may allow UI
elements to overlap.

-    PositionWindows(/* animate */ false);
-    RepositionTextFilterOnDisplayMetricsChange();
-  }
+  PositionWindows(/* animate */ false);
+  RepositionTextFilterOnDisplayMetricsChange();
 }
 
 void WindowSelector::OnWindowTreeChanged(WmWindow* window,