Cleanup Bookmarks, History, and SavedPages screen

- Redesigned bookmark thumbnail view
- Custom ImageView to scale the thumbnail properly
- Fix column count in bookmark expandable view
- Disable GroupView if we have only one account in bookmark

Change-Id: I2fccae50b9e96c909744bd5c7d0af7b373136c54
diff --git a/res/drawable/shadow_bottom.xml b/res/drawable/shadow_bottom.xml
new file mode 100644
index 0000000..b32acd7
--- /dev/null
+++ b/res/drawable/shadow_bottom.xml
@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+    * Copyright (c) 2015, The Linux Foundation. All rights reserved.
+    *
+    * Redistribution and use in source and binary forms, with or without
+    * modification, are permitted provided that the following conditions are
+    * met:
+    * * Redistributions of source code must retain the above copyright
+    * notice, this list of conditions and the following disclaimer.
+    * * Redistributions in binary form must reproduce the above
+    * copyright notice, this list of conditions and the following
+    * disclaimer in the documentation and/or other materials provided
+    * with the distribution.
+    * * Neither the name of The Linux Foundation nor the names of its
+    * contributors may be used to endorse or promote products derived
+    * from this software without specific prior written permission.
+    *
+    * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
+    * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+    * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
+    * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
+    * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+    * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+    * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+    * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+    * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+    * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
+    * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+    *
+    */
+-->
+
+<shape xmlns:android="http://schemas.android.com/apk/res/android">
+    <gradient
+        android:startColor="#20000000"
+        android:centerColor="#0A777777"
+        android:endColor="#00FFFFFF"
+        android:angle="270"/>
+</shape>
\ No newline at end of file