Add grayscale support

Bug: b/111940818
Test: test added mode under Settings-> Accessibility -> Color correction
Change-Id: I7d71152775836771ae6ebaa6af0f2e89215e744b

res/values/arrays.xml

@@ -1082,6 +1082,7 @@
         <item>daltonizer_mode_deuteranomaly</item>
         <item>daltonizer_mode_protanomaly</item>
         <item>daltonizer_mode_tritanomaly</item>
+        <item>daltonizer_mode_grayscale</item>
     </string-array>
 
     <!-- Values for display color space adjustment modes for accessibility -->
@@ -1089,6 +1090,7 @@
         <item>12</item>
         <item>11</item>
         <item>13</item>
+        <item>0</item>
     </integer-array>
 
     <!-- Battery saver mode: allowable trigger threshold levels. -->

res/values/strings.xml

@@ -5192,6 +5192,8 @@
     <string name="daltonizer_mode_protanomaly_title">Protanomaly</string>
     <!-- Title shown for tritanomaly (blue-yellow color blindness) [CHAR LIMIT=45] -->
     <string name="daltonizer_mode_tritanomaly_title">Tritanomaly</string>
+    <!-- Title shown for grayscale [CHAR LIMIT=45] -->
+    <string name="daltonizer_mode_grayscale_title">Grayscale</string>
     <!-- Summary shown for deuteranomaly (red-green color blindness) [CHAR LIMIT=45] -->
     <string name="daltonizer_mode_deuteranomaly_summary">Red-green</string>
     <!-- Summary shown for protanomaly (red-green color blindness) [CHAR LIMIT=45] -->

res/xml/accessibility_daltonizer_settings.xml

@@ -49,6 +49,10 @@
             android:persistent="false"
             android:summary="@string/daltonizer_mode_tritanomaly_summary"
             android:title="@string/daltonizer_mode_tritanomaly_title" />
+        <com.android.settingslib.widget.RadioButtonPreference
+            android:key="daltonizer_mode_grayscale"
+            android:persistent="false"
+            android:title="@string/daltonizer_mode_grayscale_title" />
 
     </PreferenceCategory>