Change GetAllDisplays() in all screens to return a const vector&.

ui/display/win/screen_win.cc

Index: ui/display/win/screen_win.cc
diff --git a/ui/display/win/screen_win.cc b/ui/display/win/screen_win.cc
index 86d6be41cd4e4a33e8a7dcc09600930582fa9e3e..9cf8660075d9cc183ee69892d49da278786ab5ac 100644
--- a/ui/display/win/screen_win.cc
+++ b/ui/display/win/screen_win.cc
@@ -384,8 +384,8 @@ int ScreenWin::GetNumDisplays() const {
   return static_cast<int>(screen_win_displays_.size());
 }
 
-std::vector<display::Display> ScreenWin::GetAllDisplays() const {
-  return ScreenWinDisplaysToDisplays(screen_win_displays_);
+const std::vector<display::Display>& ScreenWin::GetAllDisplays() const {
+  return displays_;
 }
 
 display::Display ScreenWin::GetDisplayNearestWindow(
@@ -443,6 +443,7 @@ gfx::Rect ScreenWin::DIPToScreenRectInWindow(gfx::NativeView view,
 void ScreenWin::UpdateFromDisplayInfos(
     const std::vector<DisplayInfo>& display_infos) {
   screen_win_displays_ = DisplayInfosToScreenWinDisplays(display_infos);
+  displays_ = ScreenWinDisplaysToDisplays(screen_win_displays_);
 }
 
 void ScreenWin::Initialize() {
@@ -487,7 +488,7 @@ void ScreenWin::OnWndProc(HWND hwnd,
   if (message != WM_DISPLAYCHANGE)
     return;
 
-  std::vector<display::Display> old_displays = GetAllDisplays();
+  std::vector<display::Display> old_displays = std::move(displays_);
   UpdateFromDisplayInfos(GetDisplayInfosFromSystem());
   change_notifier_.NotifyDisplaysChanged(old_displays, GetAllDisplays());

[stevenjb, 2016/11/16 22:31:07]

nit: This might be more clear if it just used displays_ instead of
GetAllDisplays().

[riajiang, 2016/11/17 22:56:53]

Done.

 }