Photo Picker Toolbar: Add UI controls showing which tile is selected.

chrome/android/java/res/layout/photo_picker_bitmap_view.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!--
      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.
 -->
 
 <!-- Represents a single item in the Photo Picker. -->
 
 <view class="org.chromium.chrome.browser.photo_picker.PickerBitmapView"
     xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="wrap_content"
-    android:layout_height="wrap_content"
-    android:background="@color/photo_picker_tile_bg_color">
+    android:layout_height="wrap_content">
 
     <FrameLayout
         android:id="@+id/border"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_gravity="center">
 
         <ImageView
             android:id="@+id/bitmap_view"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:contentDescription="@null" />
+
+        <View
+            android:id="@+id/scrim"
+            android:layout_width="64dp"
+            android:layout_height="64dp"
+            android:background="@drawable/file_picker_scrim"
+            android:visibility="gone" />
     </FrameLayout>
 
+    <ImageView
+        android:id="@+id/selected"
+        android:layout_width="24dp"
+        android:layout_height="24dp"
+        android:layout_marginStart="4dp"
+        android:layout_marginTop="4dp"
+        android:contentDescription="@null"
+        android:src="@drawable/verify_checkmark"
+        android:visibility="gone" />
+
+    <View
+        android:id="@+id/unselected"
+        android:layout_width="22dp"
+        android:layout_height="22dp"
+        android:layout_marginStart="4dp"
+        android:layout_marginTop="4dp"
+        android:background="@drawable/circle_white"
+        android:visibility="gone" />
+
     <!-- Special tiles, that give access to the camera and gallery  -->
     <TextView
         android:id="@+id/special_tile"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:layout_marginTop="@dimen/photo_picker_label_gap"
         android:drawablePadding="10dp"
         android:fontFamily="sans-serif-medium"
         android:textStyle="bold"
         android:textSize="14sp"
         android:textAllCaps="true"
         android:textColor="@color/photo_picker_special_tile_color"
         android:gravity="center"
         android:layout_gravity="center" />
 </view>