New feature “Text and reading options” for SetupWizard, Wallpaper, and Settings (12/n).

- Link-up between the preview, font size, and display size preferences.
- Add the preview preference and entry.

Bug: 211503117
Test: make RunSettingsRoboTests ROBOTEST_FILTER=TextReadingPreviewControllerTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=TextReadingPreviewPreferenceTest
Change-Id: Ic6c48861a0051670fd78b13dca5488711de30cb8

src/com/android/settings/display/PreviewPagerAdapter.java

@@ -117,7 +117,15 @@ public class PreviewPagerAdapter extends PagerAdapter {
         mAnimationEndAction = action;
     }
 
-    void setPreviewLayer(int newLayerIndex, int currentLayerIndex, int currentFrameIndex,
+    /**
+     * Switches the sample layouts for the preview pager.
+     *
+     * @param newLayerIndex the new layer index
+     * @param currentLayerIndex the current layer index
+     * @param currentFrameIndex the current frame index
+     * @param animate whether to enable the animation
+     */
+    public void setPreviewLayer(int newLayerIndex, int currentLayerIndex, int currentFrameIndex,
             final boolean animate) {
         for (FrameLayout previewFrame : mPreviewFrames) {
             if (currentLayerIndex >= 0) {