Adds WmShell::IsTouchDown()

ash/aura/wm_shell_aura.cc

Index: ash/aura/wm_shell_aura.cc
diff --git a/ash/aura/wm_shell_aura.cc b/ash/aura/wm_shell_aura.cc
index 6842682dde7c3f89ac7b3cd9e2974c1e975db46f..1881d36b4a3aa3835d67325a8ede5fee068a842a 100644
--- a/ash/aura/wm_shell_aura.cc
+++ b/ash/aura/wm_shell_aura.cc
@@ -26,6 +26,7 @@
 #include "ash/wm/window_util.h"
 #include "base/memory/ptr_util.h"
 #include "ui/aura/client/focus_client.h"
+#include "ui/aura/env.h"
 #include "ui/wm/public/activation_client.h"
 
 #if defined(OS_CHROMEOS)
@@ -214,6 +215,10 @@ void WmShellAura::RemovePointerWatcher(views::PointerWatcher* watcher) {
   Shell::GetInstance()->RemovePointerWatcher(watcher);
 }
 
+bool WmShellAura::IsTouchDown() {
+  return aura::Env::GetInstance()->is_touch_down();
+}
+
 #if defined(OS_CHROMEOS)
 void WmShellAura::ToggleIgnoreExternalKeyboard() {
   Shell::GetInstance()