arc: Implement proper Arc window activation for task moving to front.

components/exo/shell_surface.cc

 // Copyright 2015 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 "components/exo/shell_surface.h"
 
 #include "ash/aura/wm_window_aura.h"
 #include "ash/common/shell_window_ids.h"
 #include "ash/common/wm/window_resizer.h"
 #include "ash/common/wm/window_state.h"
@@ skipping 316 matching lines @@
       wm::RemoveTransientChild(parent_, widget_->GetNativeWindow());
   }
   parent_ = parent ? parent->GetWidget()->GetNativeWindow() : nullptr;
   if (parent_) {
     parent_->AddObserver(this);
     if (widget_)
       wm::AddTransientChild(parent_, widget_->GetNativeWindow());
   }
 }
 
+void ShellSurface::Activate() {
+  TRACE_EVENT0("exo", "ShellSurface::Activate");
+
+  if (!widget_ || widget_->IsActive())
+    return;
+
+  widget_->Activate();
+}
+
 void ShellSurface::Maximize() {
   TRACE_EVENT0("exo", "ShellSurface::Maximize");
 
   if (!widget_)
     CreateShellSurfaceWidget(ui::SHOW_STATE_MAXIMIZED);
 
   // Note: This will ask client to configure its surface even if already
   // maximized.
   ScopedConfigure scoped_configure(this, true);
   widget_->Maximize();
@@ skipping 888 matching lines @@
       shadow_overlay_->layer()->Add(shadow->layer());
       window->AddChild(shadow_overlay_);
       shadow_overlay_->Show();
     }
     shadow_overlay_->SetBounds(shadow_bounds);
     shadow->SetContentBounds(gfx::Rect(shadow_bounds.size()));
   }
 }
 
 }  // namespace exo