Add Preview for single select

Added support for previewing selected item.

The CL supports
1. Previewing images only, doesn't support videos
2. Preview with basic layout and doesn't completely mirror UX mocks.
3. Preview for single select, doesn't support preview for multi select

Bug: 185801129
Test: Test video is added to the bug.
Change-Id: I1edbbff3cb6467e75a17243b70378e74c8d0968b
Merged-In: I1edbbff3cb6467e75a17243b70378e74c8d0968b
(cherry picked from commit 3e52acf12b01d64af5ff5873ae9600ae65c35f6a)
diff --git a/res/values/colors.xml b/res/values/colors.xml
index 96991b0..a719570 100644
--- a/res/values/colors.xml
+++ b/res/values/colors.xml
@@ -18,8 +18,11 @@
     <color name="thumb_gray_color">#1F000000</color>
     <color name="clear_cache_icon_color">#5F6368</color>
 
-    <!-- photo picker -->
+    <!-- PhotoPicker -->
     <color name="picker_background_color">@android:color/white</color>
     <color name="picker_hairline_color">#DADCE0</color>
     <color name="picker_highlight_color">#E8F0FE</color>
+    <!-- PhotoPicker Preview -->
+    <color name="preview_add_button_background_color">#8AB4F8</color>
+    <color name="preview_buttons_text_color">#202124</color>
 </resources>