webapps: add splashscreen for installed webapps

chrome/android/java/res/values-v17/styles.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 xmlns:tools="http://schemas.android.com/tools">
     <!-- Q: Why put style resources under values-v17/ ?
          A: Problem:
             1. paddingStart causes a crash on Galaxy Tab&Note b/8351339.
             2. So we wrote a build script(generate_v14_compatible_resources.py) to convert
@@ skipping 20 matching lines @@
         <!-- Navigation Transitions, requires API level 21 -->
         <item name="android:windowAllowEnterTransitionOverlap" tools:targetApi="21">false</item>
         <item name="android:windowAllowReturnTransitionOverlap" tools:targetApi="21">true</item>
         <item name="android:windowContentTransitions" tools:targetApi="21">true</item>
         <item name="android:windowEnterTransition" tools:targetApi="21">@transition/fade</item>
         <item name="android:windowExitTransition" tools:targetApi="21">@null</item>
         <item name="android:windowSharedElementEnterTransition" tools:targetApi="21">@transition/move_image</item>
         <item name="android:windowSharedElementExitTransition" tools:targetApi="21">@transition/move_image</item>
     </style>
 
+    <style name="WebApp" parent="MainTheme">

[newt (away), 2015/07/24 19:22:04]

nit: call this WebAppTheme to distinguish it from all the "styles" in this file.
(theme != style, but they are declared in the same way :/ )

+        <item name="android:windowDisablePreview">true</item>

[David Trainor- moved to gerrit, 2015/07/24 20:39:19]

Should we be setting the window background color here?  Could we set that to the
light background color to hide the flash instead of the windowDisablePreview?

[Lalit Maganti, 2015/07/30 10:15:33]

Currently we could indeed do this. However, the idea is that in the future, the
website would specify the color in its manifest at which point we couldn't
hardcode the color in the XML.

+    </style>
+    <style name="WebAppSplashScreenTextAppearanceTitle" parent="TextAppearance.AppCompat.Title">
+        <item name="android:fontFamily">sans-serif-condensed</item>
+        <item name="android:textSize">@dimen/webapp_splash_title_size</item>
+        <item name="android:textColor">@color/webapp_splash_title</item>
+    </style>
+
     <!-- A theme for alert dialogs. The colors are copied from MainTheme, and the window
          dimensions are copied from *.MinWidth theme variants. Sadly there is no
          AppCompat.Light.Dialog.Alert or even AppCompat.Light.Dialog.MinWidth. -->
     <style name="AlertDialogTheme" parent="Theme.AppCompat.Light.Dialog">
         <item name="android:textColorHighlight">@color/text_highlight_color</item>
         <item name="android:windowMinWidthMajor">@android:dimen/dialog_min_width_major</item>
         <item name="android:windowMinWidthMinor">@android:dimen/dialog_min_width_minor</item>
 
         <!--  Overriding AppCompat values -->
         <item name="colorAccent">@color/light_active_color</item>
@@ skipping 315 matching lines @@
     <style name="LocationBarButton">
         <item name="android:background">@null</item>
     </style>
     <style name="ToolbarButton">
         <item name="android:background">?attr/selectableItemBackground</item>
         <item name="android:layout_width">48dp</item>
         <item name="android:layout_height">56dp</item>
         <item name="android:scaleType">center</item>
     </style>
 </resources>