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

ash/wm/system_gesture_event_filter.cc

Index: ash/wm/system_gesture_event_filter.cc
diff --git a/ash/wm/system_gesture_event_filter.cc b/ash/wm/system_gesture_event_filter.cc
index a3c492d6c8dc1a1ccb5864972d39df979d786912..d23325d656841887b256ba7f70fbc1de02ad2823 100644
--- a/ash/wm/system_gesture_event_filter.cc
+++ b/ash/wm/system_gesture_event_filter.cc
@@ -13,12 +13,14 @@
 #include "ash/shell_window_ids.h"
 #include "ash/wm/gestures/long_press_affordance_handler.h"
 #include "ash/wm/gestures/overview_gesture_handler.h"
+#include "ash/wm/gestures/shelf_gesture_handler.h"
 #include "ash/wm/gestures/system_pinch_handler.h"
 #include "ash/wm/window_util.h"
 #include "base/command_line.h"
 #include "ui/aura/root_window.h"
 #include "ui/base/ui_base_switches.h"
 #include "ui/events/event.h"
+#include "ui/events/event_constants.h"
 
 #if defined(OS_CHROMEOS)
 #include "ui/events/x/touch_factory_x11.h"
@@ -43,7 +45,8 @@ namespace internal {
 SystemGestureEventFilter::SystemGestureEventFilter()
     : system_gestures_enabled_(CommandLine::ForCurrentProcess()->
           HasSwitch(ash::switches::kAshEnableAdvancedGestures)),
-      long_press_affordance_(new LongPressAffordanceHandler) {
+      long_press_affordance_(new LongPressAffordanceHandler),
+      shelf_gesture_handler_(new ShelfGestureHandler()) {
   if (switches::UseOverviewMode())
     overview_gesture_handler_.reset(new OverviewGestureHandler);
 }
@@ -85,6 +88,12 @@ void SystemGestureEventFilter::OnGestureEvent(ui::GestureEvent* event) {
     return;
   }
 
+  if (event->type() == ui::ET_GESTURE_WIN8_EDGE_SWIPE &&
+      shelf_gesture_handler_->ProcessGestureEvent(*event)) {

[sadrul, 2014/02/11 21:20:48]

Do you really need an instance of the ShelfGestureHandler here? Can you just
call into Shelf::OnGestureEdgeSwipe() from here?

[zturner, 2014/02/11 21:30:57]

SystemGestureEventFilter doesn't contain an instance of the shelf, you have to
go through the ShelfGestureHandler, and we can't make the method static either. 
Unless I'm missing another way?  I think logically it makes the most sense this
way, since it doesn't stray from the accepted paradigm of having the event
filter simply forward the gesture to the appropriate handler.

[sadrul, 2014/02/11 21:37:31]

You could do: Shell::GetPrimaryRootWindowController()->GetShelfLayoutManager()?
This is true.

I don't feel strongly either way.

+    event->StopPropagation();
+    return;
+  }
+
   if (!system_gestures_enabled_)
     return;