Add ability to have active window autohide shelf

ash/common/shelf/shelf_layout_manager.cc

Index: ash/common/shelf/shelf_layout_manager.cc
diff --git a/ash/common/shelf/shelf_layout_manager.cc b/ash/common/shelf/shelf_layout_manager.cc
index f145a7ec82f3f9eb14bb1c981143f7e798aa261a..31e600ef7c1ec2b86e5bbca7418a09d3d20b9d3c 100644
--- a/ash/common/shelf/shelf_layout_manager.cc
+++ b/ash/common/shelf/shelf_layout_manager.cc
@@ -25,6 +25,7 @@
 #include "ash/public/cpp/shell_window_ids.h"
 #include "ash/root_window_controller.h"
 #include "ash/shell.h"
+#include "ash/wm/window_state_aura.h"
 #include "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/i18n/rtl.h"
@@ -243,6 +244,13 @@ void ShelfLayoutManager::UpdateVisibilityState() {
   } else if (WmShell::Get()->IsPinned()) {
     SetState(SHELF_HIDDEN);
   } else {
+    wm::WindowState* active_window = wm::GetActiveWindowState();
+
+    if (active_window && active_window->hide_shelf_when_active()) {
+      SetState(SHELF_AUTO_HIDE);
+      return;
+    }

[oshima, 2017/03/30 14:01:27]

This should happen only when the WORKSPACE_WINDOW_STATE_FULLSCREEN or
WORKSPACE_WINDOW_STATE_MAXIMIZED.

[yorkelee, 2017/03/30 19:34:12]

Done.

+
     // TODO(zelidrag): Verify shelf drag animation still shows on the device
     // when we are in SHELF_AUTO_HIDE_ALWAYS_HIDDEN.
     wm::WorkspaceWindowState window_state(