x11: Remove unneeded WeakPtr from XWindow

This is an attempt to fix or at least mitigate crash https://crbug.com/1021490.

A base::WeakPtr is used in to bind XWindow::DelayedResize task to
delayed_resize_task_, which is a CancelableCallback, which is not needed and
potentially make it harder to understand the aforementioned crash. So use
base::Unretained() instead of WeakPtr in that case.

Additionally, dcheck Close() is called before XWindow's dtor.

Bug: 1021490
Change-Id: Ibf8b2f185dc020258905f6bf5e26305c51e7a215
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1917079
Commit-Queue: Nick Yamane <nickdiego@igalia.com>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#746917}

ui/base/x/x11_window.cc

@@ -143,7 +143,10 @@ XWindow::XWindow()
   DCHECK_NE(x_root_window_, x11::None);
 }
 
-XWindow::~XWindow() = default;
+XWindow::~XWindow() {
+  DCHECK_EQ(xwindow_, x11::None) << "XWindow destructed without calling "
+                                    "Close() to release allocated resources.";
+}
 
 void XWindow::Init(const Configuration& config) {
   activatable_ = config.activatable;
@@ -1367,9 +1370,8 @@ void XWindow::DispatchResize() {
     // WM doesn't support _NET_WM_SYNC_REQUEST.
     // Or we are too slow, so _NET_WM_SYNC_REQUEST is disabled by the
     // compositor.
-    delayed_resize_task_.Reset(base::BindOnce(&XWindow::DelayedResize,
-                                              weak_factory_.GetWeakPtr(),
-                                              bounds_in_pixels_));
+    delayed_resize_task_.Reset(base::BindOnce(
+        &XWindow::DelayedResize, base::Unretained(this), bounds_in_pixels_));
     base::ThreadTaskRunnerHandle::Get()->PostTask(
         FROM_HERE, delayed_resize_task_.callback());
     return;

ui/base/x/x11_window.h

@@ -13,7 +13,6 @@
 #include "base/component_export.h"
 #include "base/containers/flat_set.h"
 #include "base/macros.h"
-#include "base/memory/weak_ptr.h"
 #include "base/optional.h"
 #include "base/strings/string16.h"
 #include "ui/gfx/geometry/insets.h"
@@ -371,14 +370,12 @@ class COMPONENT_EXPORT(UI_BASE_X) XWindow {
   bool pending_counter_value_is_extended_ = false;
   bool configure_counter_value_is_extended_ = false;
 
-  base::CancelableOnceCallback<void()> delayed_resize_task_;
+  base::CancelableOnceClosure delayed_resize_task_;
 
   // Keep track of barriers to confine cursor.
   bool has_pointer_barriers_ = false;
   std::array<XID, 4> pointer_barriers_;
 
-  base::WeakPtrFactory<XWindow> weak_factory_{this};
-
   DISALLOW_COPY_AND_ASSIGN(XWindow);
 };