Use floating labels for preference forms

chrome/android/java/res/values/dimens.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright 2014 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.
 -->
 
 <resources>
     <!-- Certificate Viewer Dimensions -->
     <dimen name="certificate_viewer_padding_wide">24dp</dimen>
     <dimen name="certificate_viewer_padding_thin">16dp</dimen>
@@ skipping 72 matching lines @@
     <dimen name="app_banner_logo_margin_end">8dp</dimen>
 
     <dimen name="app_banner_star_height">16dp</dimen>
 
     <!-- Password generation popup dimensions -->
     <dimen name="password_generation_divider_height">1dp</dimen>
     <dimen name="password_generation_text_size">14sp</dimen>
     <dimen name="password_generation_horizontal_margin">10dp</dimen>
     <dimen name="password_generation_text_vertical_margin">12dp</dimen>
 
-    <!--  Preferences button dimensions -->
-    <!-- TODO(twellington): Remove/update the following dimens after we switch the PreferencesTheme
-                                parent to AppCompat. -->
+    <!--  Preferences dimensions -->
+    <!-- TODO(twellington): Remove/update the button dimens after AppCompat adds button support. -->
     <dimen name="pref_button_margin_start">0dp</dimen>
     <dimen name="pref_button_corner_radius">2dp</dimen>
     <dimen name="pref_button_horizontal_padding">16dp</dimen>
     <dimen name="pref_button_vertical_padding">10dp</dimen>
 
+    <dimen name="pref_homepage_layout_margin">10dp</dimen>
+
     <!-- Minimum height/width for a touchable item -->
     <dimen name="min_touch_target_size">48dp</dimen>
 
     <!-- Text bubble dimensions -->
     <!-- Tooltip min distance from the edge of the screen. -->
     <dimen name="tooltip_min_edge_margin">3dp</dimen>
     <!-- Tooltip margin above click target. -->
     <dimen name="tooltip_top_margin">2dp</dimen>
     <!-- Tooltip border width around the main content bubble. -->
     <dimen name="tooltip_border_width">1dp</dimen>
@@ skipping 17 matching lines @@
     <!-- User Picture Dimensions -->
     <dimen name="user_picture_size">40dp</dimen>
     <dimen name="badged_user_picture_height">40dp</dimen>
     <!-- The design spec is that the center of the badge should be 4dp from the right edge of the
     user picture. This is equivalent to a badged_user_picture_width of 46dp assuming a badge_radius
     of 10dp. -->
     <dimen name="badged_user_picture_width">46dp</dimen>
     <dimen name="badge_radius">10dp</dimen>
     <dimen name="badge_border_size">1.3dp</dimen>
 </resources>