Fully support the autohide shelf option for touch UI on Windows.

ui/aura/remote_root_window_host_win.cc

Index: ui/aura/remote_root_window_host_win.cc
diff --git a/ui/aura/remote_root_window_host_win.cc b/ui/aura/remote_root_window_host_win.cc
index 6f95169d70b4221502d94d9104d349faff589e82..8a508a70a980b7a48a50f80203e30fa639825486 100644
--- a/ui/aura/remote_root_window_host_win.cc
+++ b/ui/aura/remote_root_window_host_win.cc
@@ -220,6 +220,7 @@ bool RemoteWindowTreeHostWin::OnMessageReceived(const IPC::Message& message) {
     IPC_MESSAGE_HANDLER(MetroViewerHostMsg_Character, OnChar)
     IPC_MESSAGE_HANDLER(MetroViewerHostMsg_WindowActivated,
                         OnWindowActivated)
+    IPC_MESSAGE_HANDLER(MetroViewerHostMsg_EdgeGesture, OnEdgeGesture)
     IPC_MESSAGE_HANDLER(MetroViewerHostMsg_TouchDown,
                         OnTouchDown)
     IPC_MESSAGE_HANDLER(MetroViewerHostMsg_TouchUp,
@@ -596,6 +597,18 @@ void RemoteWindowTreeHostWin::OnWindowActivated() {
   delegate_->OnHostActivated();
 }
 
+void RemoteWindowTreeHostWin::OnEdgeGesture() {
+  ui::GestureEvent event(
+      ui::ET_GESTURE_WIN8_EDGE_SWIPE,
+      0,
+      0,
+      0,
+      ui::EventTimeForNow(),
+      ui::GestureEventDetails(ui::ET_GESTURE_WIN8_EDGE_SWIPE, 0, 0),
+      0);
+  SendEventToProcessor(&event);
+}
+
 void RemoteWindowTreeHostWin::OnTouchDown(int32 x,
                                           int32 y,
                                           uint64 timestamp,