Updates for the look of the bookmarks page.

Add new assets.

-tab_indicator.xml
State selector for the background of tabs in the CombinedHistoryActivity

-bookmark_thumnail.xml
Web page title is now above the thumb.  Removed the favicon.  Added a
shadow.

-tab_header.xml
Layout for the tabs in CombinedHistoryActivity

-tabs.xml
Change the height of the tabs.

-bookmarks.xml
Remove the title for the "switch" menu item, which gets set in Java,
depending on the current viewing mode.

-strings.xml
Remove the placeholder menu item text, add the actual text for
switching between modes.

-BrowserBookmarksAdapter
No longer set the favicon on top of the bookmark thumbs in grid mode.

-BrowserBookmarksPage
Implement onPrepareOptionsMenu, and set the title of a menu option,
depending on the current viewing state.

-CombinedHistoryActivity
Create a common function for setting up all the tabs.  Change the
look of the tabs to match the new design.
diff --git a/res/values/strings.xml b/res/values/strings.xml
index c600666..47f1a60 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -169,9 +169,12 @@
             currently on, but is not visible because the bookmarks page is 
             showing. -->
     <string name="bookmark_page">Bookmark last-viewed page</string>
-    <!-- Menu item in the page that displays all bookmarks.  Switches between
-            a vertical list view and a grid view which shows thumbnails -->
-    <string name="switch_mode">Switch viewing mode</string>
+    <!-- Menu item in the page that displays all bookmarks.  Switches to
+            a grid view which shows thumbnails -->
+    <string name="switch_to_thumbnails">Thumbnail view</string>
+    <!-- Menu item in the page that displays all bookmarks.  Switches to a
+            list view which shows titles -->
+    <string name="switch_to_list">List view</string>
     <!-- Summary text under the New Bookmark item on the Bookmarks screen.
             Tells the user that if they select this item, it will bring up a
             dialog to bookmark the page that the browser is currently viewing,