Misc fix on settings themes.

- Use dark status bar for confirmDeviceCreditials theme to match dark
  window background
- Remove SubSettingsDialogWhenLarge theme in favor of full screen
  settings for O.
- Update font/dize preview text color to match light background

Bug: 33558692
Test: visual

Change-Id: Id8704c96e2ce35247e80e50eefd531786479b193
diff --git a/src/com/android/settings/SettingsActivity.java b/src/com/android/settings/SettingsActivity.java
index 13bc048..c01e4c4 100644
--- a/src/com/android/settings/SettingsActivity.java
+++ b/src/com/android/settings/SettingsActivity.java
@@ -387,14 +387,10 @@
         final boolean isSubSettings = this instanceof SubSettings ||
                 intent.getBooleanExtra(EXTRA_SHOW_FRAGMENT_AS_SUBSETTING, false);
 
-        // If this is a sub settings, then apply the SubSettings Theme for the ActionBar content insets
+        // If this is a sub settings, then apply the SubSettings Theme for the ActionBar content
+        // insets
         if (isSubSettings) {
-            // Check also that we are not a Theme Dialog as we don't want to override them
-            final int themeResId = getThemeResId();
-            if (themeResId != R.style.Theme_DialogWhenLarge &&
-                    themeResId != R.style.Theme_SubSettingsDialogWhenLarge) {
-                setTheme(R.style.Theme_SubSettings);
-            }
+            setTheme(R.style.Theme_SubSettings);
         }
 
         setContentView(mIsShowingDashboard ?