Fix grabbing capture when the mouse is pressed on Desktop Linux.

ui/base/x/x11_util.h

Index: ui/base/x/x11_util.h
diff --git a/ui/base/x/x11_util.h b/ui/base/x/x11_util.h
index ffcf8461c75613fe43ba39aeec23b08db6c298ed..448d3257b9b86c519057e8d1505589da4f40ce03 100644
--- a/ui/base/x/x11_util.h
+++ b/ui/base/x/x11_util.h
@@ -45,6 +45,12 @@ namespace ui {
 // Returns true if the system supports XINPUT2.
 UI_BASE_EXPORT bool IsXInput2Available();
 
+// Grabs the pointer.
+UI_BASE_EXPORT int GrabPointer(XID window, bool owner_events, ::Cursor cursor);
+
+// Ungrabs the pointer.
+UI_BASE_EXPORT void UngrabPointer();

[sadrul, 2014/12/22 21:08:59]

Would it be possible to have something like ScopedGrabPointer? So that the
caller of GrabPointer() receives a ScopedGrabPointer object, and resets it to
ungrab. This makes sure some code doesn't accidentally forget to ungrab, and
doesn't try to ungrab when it doesn't have a grab.

+
 // X shared memory comes in three flavors:
 // 1) No SHM support,
 // 2) SHM putimage,