X11: Handle change notify for _NET_WORKAREA

ui/views/widget/desktop_aura/desktop_screen_x11.cc

Index: ui/views/widget/desktop_aura/desktop_screen_x11.cc
diff --git a/ui/views/widget/desktop_aura/desktop_screen_x11.cc b/ui/views/widget/desktop_aura/desktop_screen_x11.cc
index 6ffd94a3c896909e26a399f93b380d9123bd01e7..9ccbe0ad190ce1f14ab4762588303091002c2a10 100644
--- a/ui/views/widget/desktop_aura/desktop_screen_x11.cc
+++ b/ui/views/widget/desktop_aura/desktop_screen_x11.cc
@@ -33,6 +33,11 @@
 
 namespace {
 
+const char* const kAtomsToCache[] = {
+  "_NET_WORKAREA",
+  nullptr
+};
+
 // The delay to perform configuration after RRNotify.  See the comment
 // in |Dispatch()|.
 const int64_t kConfigureDelayMs = 500;
@@ -86,7 +91,8 @@ DesktopScreenX11::DesktopScreenX11()
     : xdisplay_(gfx::GetXDisplay()),
       x_root_window_(DefaultRootWindow(xdisplay_)),
       has_xrandr_(false),
-      xrandr_event_base_(0) {
+      xrandr_event_base_(0),
+      atom_cache_(xdisplay_, kAtomsToCache) {
   // We only support 1.3+. There were library changes before this and we should
   // use the new interface instead of the 1.2 one.
   int randr_version_major = 0;
@@ -229,14 +235,19 @@ void DesktopScreenX11::RemoveObserver(gfx::DisplayObserver* observer) {
 
 bool DesktopScreenX11::CanDispatchEvent(const ui::PlatformEvent& event) {
   return event->type - xrandr_event_base_ == RRScreenChangeNotify ||
-         event->type - xrandr_event_base_ == RRNotify;
+         event->type - xrandr_event_base_ == RRNotify ||
+         (event->type == PropertyNotify &&
+          event->xproperty.window == x_root_window_ &&
+          event->xproperty.atom == atom_cache_.GetAtom("_NET_WORKAREA"));
 }
 
 uint32_t DesktopScreenX11::DispatchEvent(const ui::PlatformEvent& event) {
   if (event->type - xrandr_event_base_ == RRScreenChangeNotify) {
     // Pass the event through to xlib.
     XRRUpdateConfiguration(event);
-  } else if (event->type - xrandr_event_base_ == RRNotify) {
+  } else if (event->type - xrandr_event_base_ == RRNotify ||
+             (event->type == PropertyNotify &&
+              event->xproperty.atom == atom_cache_.GetAtom("_NET_WORKAREA"))) {
     // There's some sort of observer dispatch going on here, but I don't think
     // it's the screen's?
     if (configure_timer_.get() && configure_timer_->IsRunning()) {
@@ -272,7 +283,8 @@ DesktopScreenX11::DesktopScreenX11(
       x_root_window_(DefaultRootWindow(xdisplay_)),
       has_xrandr_(false),
       xrandr_event_base_(0),
-      displays_(test_displays) {
+      displays_(test_displays),
+      atom_cache_(xdisplay_, kAtomsToCache) {
 }
 
 std::vector<gfx::Display> DesktopScreenX11::BuildDisplaysFromXRandRInfo() {