cros: Use runtime stylus detection for ash palette.

ash/common/system/chromeos/palette/palette_utils.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/common/system/chromeos/palette/palette_utils.h"
 
 #include "ash/common/ash_switches.h"
 #include "ash/common/shelf/wm_shelf.h"
 #include "ash/common/system/chromeos/palette/palette_tray.h"
 #include "ash/common/system/status_area_widget.h"
 #include "ash/common/wm_shell.h"
 #include "ash/common/wm_window.h"
 #include "base/command_line.h"
+#include "ui/events/devices/input_device_manager.h"
+#include "ui/events/devices/touchscreen_device.h"
 #include "ui/gfx/geometry/point.h"
 
 namespace ash {
 
-bool IsPaletteFeatureEnabled() {
-  return base::CommandLine::ForCurrentProcess()->HasSwitch(
-      switches::kAshEnablePalette);
+bool HasStylusInput() {
+  // Allow the user to force-enable by passing a switch.
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kAshEnablePalette)) {

[stevenjb, 2017/01/21 00:23:50]

This switch name is now a bit unfortunate, it seems like it should be something
like kAshForceEnablePalette. (I.e. it sounds like without the switch this would
always return false).

[jdufault, 2017/01/25 00:53:15]

I've renamed the switch.

+    return true;
+  }
+
+  for (const ui::TouchscreenDevice& device :
+       ui::InputDeviceManager::GetInstance()->GetTouchscreenDevices()) {
+    if (device.is_stylus &&
+        device.type == ui::InputDeviceType::INPUT_DEVICE_INTERNAL) {
+      return true;
+    }
+  }
+
+  return false;
 }
 
 bool IsPaletteEnabledOnEveryDisplay() {
   return base::CommandLine::ForCurrentProcess()->HasSwitch(
       switches::kAshEnablePaletteOnAllDisplays);
 }
 
 bool PaletteContainsPointInScreen(const gfx::Point& point) {
   for (WmWindow* window : WmShell::Get()->GetAllRootWindows()) {
     PaletteTray* palette_tray =
         WmShelf::ForWindow(window)->GetStatusAreaWidget()->palette_tray();
     if (palette_tray && palette_tray->ContainsPointInScreen(point))
       return true;
   }
 
   return false;
 }
 
 }  // namespace ash