Add support for webapk without runtimeHost

chrome/android/webapk/shell_apk/res/color/item_selection_text_color.xml

Index: chrome/android/webapk/shell_apk/res/color/item_selection_text_color.xml
diff --git a/chrome/android/webapk/shell_apk/res/color/item_selection_text_color.xml b/chrome/android/webapk/shell_apk/res/color/item_selection_text_color.xml
new file mode 100644
index 0000000000000000000000000000000000000000..dcf78833f1dcb85efce53298c234a140688f1f99
--- /dev/null
+++ b/chrome/android/webapk/shell_apk/res/color/item_selection_text_color.xml
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>

[Ted C, 2017/06/05 18:24:48]

did you try:
https://developer.android.com/reference/android/R.color.html#primary_text_dark
  or
https://developer.android.com/reference/android/R.color.html#primary_text_light

They might be indistinguishable if you want to eke a tiny bit of improvement.

[Xi Han, 2017/06/05 20:30:02]

The primary_text_dark looks too light for the enabled text, and black looks
closer to the color in the UI
review(https://docs.google.com/presentation/d/1ZC7Fc9Y7-vsGqvbEyiZmiJoWtsONkhPBUb47F0s4u4s/edit#slide=id.g1ca70aafc8_0_16).
However, it seems using @android:color/primary_text_light can't change the color
of the disabled text which is still black. So I remove this xml, and just set
the text color programmatically.

+<!-- Copyright 2017 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. -->
+
+<selector xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:state_enabled="false" android:color="#808080" />
+    <item android:color="#000000"/>
+</selector>