Enable setting capture to a non-toplevel widget when the widget is activated on Linux

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 7ceac3af3ee7c0f72158cef9c249c744c9008376..92dc54ee3a60b78708a6c4cae8b212edb38b11af 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
@@ -205,6 +205,8 @@ void DesktopWindowTreeHostX11::HandleNativeWidgetActivationChanged(
     OnHostActivated();
     open_windows().remove(xwindow_);
     open_windows().insert(open_windows().begin(), xwindow_);
+  } else {
+    ReleaseCapture();
   }
 
   desktop_native_widget_aura_->HandleActivationChanged(active);
@@ -313,7 +315,7 @@ void DesktopWindowTreeHostX11::CloseNow() {
   if (xwindow_ == None)
     return;
 
-  x11_capture_.reset();
+  ReleaseCapture();
   native_widget_delegate_->OnNativeWidgetDestroying();
 
   // If we have children, close them. Use a copy for iteration because they'll
@@ -510,7 +512,7 @@ void DesktopWindowTreeHostX11::Deactivate() {
   if (!IsActive())
     return;
 
-  x11_capture_.reset();
+  ReleaseCapture();
   X11DesktopHandler::get()->DeactivateWindow(xwindow_);
 }
 
@@ -532,7 +534,7 @@ void DesktopWindowTreeHostX11::Maximize() {
 }
 
 void DesktopWindowTreeHostX11::Minimize() {
-  x11_capture_.reset();
+  ReleaseCapture();
   XIconifyWindow(xdisplay_, xwindow_, 0);
 }
 
@@ -821,10 +823,8 @@ void DesktopWindowTreeHostX11::OnNativeWidgetFocus() {
 }
 
 void DesktopWindowTreeHostX11::OnNativeWidgetBlur() {
-  if (xwindow_) {
-    x11_capture_.reset();

[sadrul, 2014/07/14 16:58:00]

Can you explain this change?

[pkotwicz, 2014/07/14 18:25:20]

This line in particular made it pointless to grab capture when a non-toplevel
widget got activated (because the toplevel widget would lose focus killing the
capture which was just set)

Note that the order of events is:
1) old window loses activation
2) new window gains activation
3) old window loses focus
4) new window gains focus

I think that the intent of the code is to release capture when we are
deactivated. I have modified HandleNativeWidgetActivationChanged() to do just
that

The reason that I changed x11_capture_.reset() to ReleaseCapture() in this CL is
that the test that I wrote would pass with or without this CL (due to the fact
that the effect of x11_capture_.reset() is asynchronous. Using ReleaseCapture()
makes the test actually useful.

+  if (xwindow_)
     native_widget_delegate_->AsWidget()->GetInputMethod()->OnBlur();
-  }
 }
 
 bool DesktopWindowTreeHostX11::IsAnimatingClosed() const {