Make Page Visibility API work when the browser window is visible or not

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index 146355707f08f247446929d5c6c0d22d7b5e11e2..ba754244328f44e716b858e103d96fd63d301ca5 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -1430,6 +1430,12 @@ void RenderWidgetHostViewAura::UnlockMouse() {
   host_->LostMouseLock();
 }
 
+void RenderWidgetHostViewAura::SetWindowVisibility(bool visible) {
+  if (host_)
+    host_->Send(new ViewMsg_SetWindowVisibility(host_->GetRoutingID(),
+        visible));
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // RenderWidgetHostViewAura, ui::TextInputClient implementation:
 void RenderWidgetHostViewAura::SetCompositionText(
@@ -2276,6 +2282,10 @@ void RenderWidgetHostViewAura::OnHostMoved(const aura::WindowTreeHost* host,
   UpdateScreenInfo(window_);
 }
 
+void RenderWidgetHostViewAura::OnHostSetWindowVisibility(
+    const aura::WindowTreeHost* host, bool visible) {
+  SetWindowVisibility(visible);
+}
 ////////////////////////////////////////////////////////////////////////////////
 // RenderWidgetHostViewAura, private: