cros: Use runtime stylus detection for ash palette.

chrome/browser/ui/webui/options/chromeos/options_stylus_handler.cc

Index: chrome/browser/ui/webui/options/chromeos/options_stylus_handler.cc
diff --git a/chrome/browser/ui/webui/options/chromeos/options_stylus_handler.cc b/chrome/browser/ui/webui/options/chromeos/options_stylus_handler.cc
index d832ba9f4ca39872344dc3608055bff4d4ef7ab5..a478e0e6c6e8243b3b91caefa5a3146f790800b6 100644
--- a/chrome/browser/ui/webui/options/chromeos/options_stylus_handler.cc
+++ b/chrome/browser/ui/webui/options/chromeos/options_stylus_handler.cc
@@ -61,8 +61,7 @@ void OptionsStylusHandler::GetLocalizedValues(
       l10n_util::GetStringUTF16(
           IDS_OPTIONS_STYLUS_NOTE_TAKING_APP_WAITING_FOR_ANDROID));
 
-  localized_strings->SetBoolean("showStylusSettings",
-                                ash::IsPaletteFeatureEnabled());
+  localized_strings->SetBoolean("showStylusSettings", ash::HasStylusInput());

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

Do we need an observer now to set this if it changes?

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

Technically, yes, but I think the only time this would be a problem is if
settings opens and loads immediately on login after the Chrome binary has
restarted (either from a crash or the user has custom flags set).

One issue with dynamically changing this value is that page initialization
currently does not support showing a section dynamically. I think this could be
fixed though without too much hassle - it'll probably involve adding a new
callback from C++ -> JS though.

I can fix these problems, if you think addressing this edge-case is worthwhile.

[stevenjb, 2017/01/25 01:12:13]

Custom flags are not too uncommon, so this really depends on how
ash::HasStylusInput() is implemented (I think I saw but I don't remember and
can't find it just now). If there is a reasonable chance that loading settings
right away might have an incorrect result, we should add the observer and a C++
-> JS method. If it is only theoretical we can get away with just adding a
comment.

[jdufault, 2017/02/03 20:30:19]

If Chrome browser process crashed and immediately reloaded one of the settings
pages on startup, the stylus settings failed to display. I've implemented some
observers that in options/settings that fix this case.

 }
 
 void OptionsStylusHandler::InitializePage() {