Avoid blocking while mapping an X11 window

ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc

Index: ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
index 3b848bc9ddb9aa899dc8eaf96f30a0a97998e5b1..920e0a31bb0d20d3ace1c2ad8b6981818f5b1cce 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
@@ -188,7 +188,7 @@ DesktopWindowTreeHostX11::DesktopWindowTreeHostX11(
       x_root_window_(DefaultRootWindow(xdisplay_)),
       atom_cache_(xdisplay_, kAtomsToCache),
       window_mapped_(false),
-      wait_for_unmap_(false),
+      is_visible_(false),
       is_fullscreen_(false),
       is_always_on_top_(false),
       use_native_frame_(false),
@@ -593,7 +593,7 @@ void DesktopWindowTreeHostX11::ShowMaximizedWithBounds(
 }
 
 bool DesktopWindowTreeHostX11::IsVisible() const {
-  return window_mapped_ && !wait_for_unmap_;
+  return is_visible_;
 }
 
 void DesktopWindowTreeHostX11::SetSize(const gfx::Size& requested_size) {
@@ -1214,7 +1214,7 @@ void DesktopWindowTreeHostX11::ShowImpl() {
 void DesktopWindowTreeHostX11::HideImpl() {
   if (IsVisible()) {
     XWithdrawWindow(xdisplay_, xwindow_, 0);

[Daniel Erat, 2017/03/09 15:07:22]

this also unmaps the window, right? is there a reason why we don't set
window_mapped_ to false here and instead wait for UnmapNotify?

[Tom (Use chromium acct), 2017/03/10 01:29:57]

Before, we had wait_for_unmap_ that sort of did this.  But, now there's no point
in adding a BlockUntilWindowUnmapped

-    wait_for_unmap_ = true;
+    is_visible_ = false;
   }
   native_widget_delegate_->OnNativeWidgetVisibilityChanged(false);
 }
@@ -1232,9 +1232,12 @@ void DesktopWindowTreeHostX11::SetBoundsInPixels(
   XWindowChanges changes = {0};
   unsigned value_mask = 0;
 
-  delayed_resize_task_.Cancel();
 
   if (size_changed) {
+    // Only cancel the delayed resize task if we're already about to call
+    // OnHostResized in this function.
+    delayed_resize_task_.Cancel();
+
     // Update the minimum and maximum sizes in case they have changed.
     UpdateMinAndMaxSize();
 
@@ -1654,9 +1657,6 @@ void DesktopWindowTreeHostX11::OnFrameExtentsUpdated() {
 }
 
 void DesktopWindowTreeHostX11::UpdateMinAndMaxSize() {
-  if (!IsVisible())
-    return;
-
   gfx::Size minimum_in_pixels =
       ToPixelRect(gfx::Rect(native_widget_delegate_->GetMinimumSize())).size();
   gfx::Size maximum_in_pixels =
@@ -1927,19 +1927,10 @@ void DesktopWindowTreeHostX11::MapWindow(ui::WindowShowState show_state) {
   ui::X11EventSource* event_source = ui::X11EventSource::GetInstance();
   DCHECK(event_source);
 
-  if (wait_for_unmap_) {
-    // Block until our window is unmapped. This avoids a race condition when
-    // remapping an unmapped window.
-    event_source->BlockUntilWindowUnmapped(xwindow_);
-    DCHECK(!wait_for_unmap_);
-  }
+  UpdateMinAndMaxSize();
 
   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.
-  event_source->BlockUntilWindowMapped(xwindow_);
+  is_visible_ = true;
 }
 
 void DesktopWindowTreeHostX11::SetWindowTransparency() {
@@ -2167,8 +2158,6 @@ uint32_t DesktopWindowTreeHostX11::DispatchEvent(
       for (DesktopWindowTreeHostObserverX11& observer : observer_list_)
         observer.OnWindowMapped(xwindow_);
 
-      UpdateMinAndMaxSize();
-
       // Some WMs only respect maximize hints after the window has been mapped.
       // Check whether we need to re-do a maximization.
       if (should_maximize_after_map_) {
@@ -2180,7 +2169,6 @@ uint32_t DesktopWindowTreeHostX11::DispatchEvent(
     }
     case UnmapNotify: {
       window_mapped_ = false;
-      wait_for_unmap_ = false;
       has_pointer_ = false;
       has_pointer_grab_ = false;
       has_pointer_focus_ = false;