Return the primary display when the view doesn't have a window associated with it.

Bug: 769754
Change-Id: I909fed33dd12215b30c13b5d5c913337b56ef717
Reviewed-on: https://chromium-review.googlesource.com/690656Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Lucas Gadani <lfg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505346}

ui/display/win/screen_win.cc

@@ -415,6 +415,8 @@ const std::vector<Display>& ScreenWin::GetAllDisplays() const {
 }
 
 Display ScreenWin::GetDisplayNearestWindow(gfx::NativeWindow window) const {
+  if (!window)
+    return GetPrimaryDisplay();
   HWND window_hwnd = GetHWNDFromNativeView(window);
   if (!window_hwnd) {
     // When |window| isn't rooted to a display, we should just return the