cros: Use runtime stylus detection for ash palette.

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

 // Copyright (c) 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 "chrome/browser/ui/webui/options/chromeos/options_stylus_handler.h"
 
 #include "ash/common/system/chromeos/palette/palette_utils.h"
 #include "base/values.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/grit/generated_resources.h"
@@ skipping 43 matching lines @@
       l10n_util::GetStringUTF16(IDS_OPTIONS_STYLUS_NOTE_TAKING_APP_LABEL));
   localized_strings->SetString(
       "stylusNoteTakingAppNoneAvailable",
       l10n_util::GetStringUTF16(
           IDS_OPTIONS_STYLUS_NOTE_TAKING_APP_NONE_AVAILABLE));
   localized_strings->SetString(
       "stylusNoteTakingAppWaitingForAndroid",
       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() {
   UpdateNoteTakingApps();
 }
 
 void OptionsStylusHandler::RegisterMessages() {
   web_ui()->RegisterMessageCallback(
       "setPreferredNoteTakingApp",
       base::Bind(&OptionsStylusHandler::SetPreferredNoteTakingApp,
@@ skipping 45 matching lines @@
     LOG(ERROR) << "Got unknown note-taking-app ID \"" << app_id << "\"";
     return;
   }
 
   NoteTakingHelper::Get()->SetPreferredApp(Profile::FromWebUI(web_ui()),
                                            app_id);
 }
 
 }  // namespace options
 }  // namespace chromeos