Remove ui::X11EventSource::BlockUntilWindowMapped

This CL removes BlockUntilWindowMapped() and the 2 references to it.

The first reference, in X11WholeScreenMoveLoop, waits until an offscreen window
is mapped.  The window is override-redirect (so there's not WM that
asynchronously decides when to map the window), so any operations done on the
window should succeed after the window is mapped since the X server processes
events in sequence.

The second reference is from X11WindowBase.  A similar removal was done in
DesktopWindowTreeHostX11 in [1], so BlockUntilWindowMapped() shouldn't be needed
here either.

[1] https://chromium.googlesource.com/chromium/src/+/662c24fc6debb33ee34a927d21dc26154b8973d6

R=sadrul@chromium.org

Change-Id: I251e67839dd5216f5164a103a82ad8a906811a03
Bug: None
Reviewed-on: https://chromium-review.googlesource.com/823212
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#525869}

ui/events/platform/x11/x11_event_source.cc

@@ -143,10 +143,6 @@ void X11EventSource::DispatchXEventNow(XEvent* event) {
   ExtractCookieDataDispatchEvent(event);
 }
 
-void X11EventSource::BlockUntilWindowMapped(XID window) {
-  BlockOnWindowStructureEvent(window, MapNotify);
-}
-
 Time X11EventSource::GetCurrentServerTime() {
   DCHECK(display_);
 
@@ -276,16 +272,6 @@ void X11EventSource::PostDispatchEvent(XEvent* xevent) {
   }
 }
 
-void X11EventSource::BlockOnWindowStructureEvent(XID window, int type) {
-  XEvent event;
-  do {
-    // Block until there's a StructureNotify event of |type| on |window|. Then
-    // remove it from the queue and stuff it in |event|.
-    XWindowEvent(display_, window, StructureNotifyMask, &event);
-    ExtractCookieDataDispatchEvent(&event);
-  } while (event.type != type);
-}
-
 void X11EventSource::StopCurrentEventStream() {
   continue_stream_ = false;
 }

ui/events/platform/x11/x11_event_source.h

@@ -62,17 +62,6 @@ class EVENTS_EXPORT X11EventSource {
   // main X11 event loop.
   void DispatchXEventNow(XEvent* event);
 
-  // Blocks on the X11 event queue until we receive notification from the
-  // xserver that |w| has been mapped; StructureNotifyMask events on |w| are
-  // pulled out from the queue and dispatched out of order.
-  //
-  // For those that know X11, this is really a wrapper around XWindowEvent
-  // which still makes sure the preempted event is dispatched instead of
-  // dropped on the floor. This method exists because mapping a window is
-  // asynchronous (and we receive an XEvent when mapped), while there are also
-  // functions which require a mapped window.
-  void BlockUntilWindowMapped(XID window);
-
   XDisplay* display() { return display_; }
 
   // Returns the timestamp of the event currently being dispatched.  Falls back
@@ -96,10 +85,6 @@ class EVENTS_EXPORT X11EventSource {
   // Handles updates after event has been dispatched.
   void PostDispatchEvent(XEvent* xevent);
 
-  // Block until receiving a structure notify event of |type| on |window|.
-  // Dispatch all encountered events prior to the one we're blocking on.
-  void BlockOnWindowStructureEvent(XID window, int type);
-
   // Explicitly asks the X11 server for the current timestamp, and updates
   // |last_seen_server_time_| with this value.
   Time GetCurrentServerTime();

ui/platform_window/x11/x11_window_base.cc

@@ -144,18 +144,13 @@ void X11WindowBase::Show() {
     return;
 
   XMapWindow(xdisplay_, xwindow_);
-
-  // We now block until our window is mapped. Some X11 APIs will crash and
-  // burn if passed |xwindow_| before the window is mapped, and XMapWindow is
-  // asynchronous.
-  if (X11EventSource::GetInstance())
-    X11EventSource::GetInstance()->BlockUntilWindowMapped(xwindow_);
   window_mapped_ = true;
 }
 
 void X11WindowBase::Hide() {
   if (!window_mapped_)
     return;
+
   XWithdrawWindow(xdisplay_, xwindow_, 0);
   window_mapped_ = false;
 }

ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc

@@ -275,7 +275,6 @@ void X11WholeScreenMoveLoop::CreateDragInputWindow(XDisplay* display) {
       new ui::XScopedEventSelector(grab_input_window_, event_mask));
 
   XMapRaised(display, grab_input_window_);
-  ui::X11EventSource::GetInstance()->BlockUntilWindowMapped(grab_input_window_);
 }
 
 }  // namespace views