linux-aura: Fix some dragging behaviour.

ui/views/widget/desktop_aura/x11_scoped_capture.cc

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/views/widget/desktop_aura/x11_scoped_capture.h"
+
+#include <X11/X.h>
+#include <X11/Xlib.h>
+
+#include "ui/gfx/x/x11_types.h"
+
+namespace views {
+
+X11ScopedCapture::X11ScopedCapture(XID window)
+    : captured_(false) {
+  // TODO(sad): Use XI2 API instead.
+  unsigned int event_mask = PointerMotionMask | ButtonReleaseMask |
+                            ButtonPressMask;
+  int status = XGrabPointer(gfx::GetXDisplay(), window, True, event_mask,
+                            GrabModeAsync, GrabModeAsync, None, None,
+                            CurrentTime);
+  captured_ = status == GrabSuccess;
+}
+
+X11ScopedCapture::~X11ScopedCapture() {
+  if (captured_) {
+    XUngrabPointer(gfx::GetXDisplay(), CurrentTime);
+  }
+}
+
+}  // namespace views