A window should not get activated or get input focus if it's behind the lock screen.

ui/views/widget/native_widget_aura.cc

 // Copyright (c) 2012 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/native_widget_aura.h"
 
 #include "base/bind.h"
 #include "base/strings/string_util.h"
 #include "build/build_config.h"
 #include "third_party/skia/include/core/SkRegion.h"
@@ skipping 473 matching lines @@
   if (!window_)
     return;
 
   if (state == ui::SHOW_STATE_MAXIMIZED || state == ui::SHOW_STATE_FULLSCREEN ||
       state == ui::SHOW_STATE_DOCKED) {
     window_->SetProperty(aura::client::kShowStateKey, state);
   }
   window_->Show();
   if (delegate_->CanActivate()) {
     if (state != ui::SHOW_STATE_INACTIVE)
       Activate();

[sky, 2016/03/04 16:32:55]

I was thinking that in this branch you would see if Activate() failed you would
change the state here. And add a comment as to why that happens.

[xdai1, 2016/03/04 22:27:28]

I see your point now. So in order to make this change
(NativeWidgetAura::Activate() returns bool type), below is the list of functions
we also need to change. I just want to confirm with you before making this
change. If it looks good to you, I'll go ahead. Thanks for your help.

NativeWidgetPrivate::Activate()
  NativeWidgetAura::Activate()
    ActivationClient::ActivateWindow()
      DefaultActivationClient::ActivateWindow()
        DefaultActivationClient::ActivateWindowImpl()
      FocusClient::FocusWindow()
        FocusController::ActivateWindow()
          FocusController::FocusWindow()
            FocusController::FocusAndActivateWindow()
  DesktopNativeWidgetAura::Activate()
    DesktopWindowTreeHost::Activate()
      DesktopWindowTreeHostX11::Activate()
  NativeWidgetMus::Activate()

     // SetInitialFocus() should be always be called, even for
     // SHOW_STATE_INACTIVE. If the window has to stay inactive, the method will
     // do the right thing.
-    SetInitialFocus(state);
+    SetInitialFocus(wm::CanActivateWindow(window_) ? state
+                                                   : ui::SHOW_STATE_INACTIVE);
   }
 
   // On desktop aura, a window is activated first even when it is shown as
   // minimized. Do the same for consistency.
   if (state == ui::SHOW_STATE_MINIMIZED)
     Minimize();
 }
 
 bool NativeWidgetAura::IsVisible() const {
   return window_ && window_->IsVisible();
@@ skipping 658 matching lines @@
   l10n_util::AdjustUIFont(&(ncm.lfCaptionFont));
   base::win::ScopedHFONT caption_font(CreateFontIndirect(&(ncm.lfCaptionFont)));
   return gfx::FontList(gfx::Font(caption_font.get()));
 #else
   return gfx::FontList();
 #endif
 }
 
 }  // namespace internal
 }  // namespace views