cros: Use runtime stylus detection for ash palette.

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

Index: ash/common/system/chromeos/palette/palette_utils.cc
diff --git a/ash/common/system/chromeos/palette/palette_utils.cc b/ash/common/system/chromeos/palette/palette_utils.cc
index 28f61d308880e09c765572d6d12d1b3bfdffd1f8..0214f209b10cea57332bf8e2617180051acc8fc3 100644
--- a/ash/common/system/chromeos/palette/palette_utils.cc
+++ b/ash/common/system/chromeos/palette/palette_utils.cc
@@ -11,13 +11,28 @@
 #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() {