[Android] Change checkable_image_view_widget size

This CL increases CheckableImageView size specified in
checkable_image_view_widget.xml to match the size of standard checkbox
widget and fix alignment.

Bug: 857267
Change-Id: I6beb61a6d7d27092b3a491b3e8e2c9ee962f69ae
Reviewed-on: https://chromium-review.googlesource.com/1118272Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Boris Sazonov <bsazonov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571126}

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

@@ -5,5 +5,6 @@
 <org.chromium.ui.widget.CheckableImageView
     xmlns:android="http://schemas.android.com/apk/res/android"
     android:id="@+id/checkable_image_view"
-    android:layout_width="wrap_content"
-    android:layout_height="wrap_content"/>
+    android:layout_width="32dp"
+    android:layout_height="32dp"
+    android:scaleType="center"/>