Define the assistive API preferences for Assistive features

The preferences are used to define persistent storage of maps of strings to boolean values
which can be used for implementing crbug.com/1060965 and other assistive features.

Change-Id: Ibe93ac0f4ec85333840d3e9a8547ebee4a445d9b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2126429
Commit-Queue: Keith Lee <keithlee@chromium.org>
Reviewed-by: Darren Shen <shend@chromium.org>
Reviewed-by: Keith Lee <keithlee@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#769630}

chrome/browser/chromeos/preferences.cc

@@ -276,6 +276,8 @@ void Preferences::RegisterProfilePrefs(
   registry->RegisterStringPref(::prefs::kLanguagePreloadEngines,
                                hardware_keyboard_id);
   registry->RegisterStringPref(::prefs::kLanguageEnabledImes, "");
+  registry->RegisterDictionaryPref(
+      chromeos::prefs::kAssistiveInputFeatureSettings);
   registry->RegisterDictionaryPref(
       ::prefs::kLanguageInputMethodSpecificSettings);
 

chromeos/constants/chromeos_pref_names.cc

@@ -7,6 +7,10 @@
 namespace chromeos {
 namespace prefs {
 
+// Map of strings to values used for assistive input settings.
+const char kAssistiveInputFeatureSettings[] =
+    "assistive_input_feature_settings";
+
 // A dictionary pref to hold the mute setting for all the currently known
 // audio devices.
 const char kAudioDevicesMute[] = "settings.audio.devices.mute";

chromeos/constants/chromeos_pref_names.h

@@ -10,6 +10,8 @@
 namespace chromeos {
 namespace prefs {
 
+COMPONENT_EXPORT(CHROMEOS_CONSTANTS)
+extern const char kAssistiveInputFeatureSettings[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS) extern const char kAudioDevicesMute[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS)
 extern const char kAudioDevicesVolumePercent[];