webapps: add splashscreen for installed webapps

chrome/android/java/res/values-v17/styles.xml

Index: chrome/android/java/res/values-v17/styles.xml
diff --git a/chrome/android/java/res/values-v17/styles.xml b/chrome/android/java/res/values-v17/styles.xml
index a711f4f4dafbeb88bb802608a1ed7f010c02bf29..653d67ea167c46a1e42f7c13ab2e8c3282745859 100644
--- a/chrome/android/java/res/values-v17/styles.xml
+++ b/chrome/android/java/res/values-v17/styles.xml
@@ -38,6 +38,15 @@
         <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. -->