WebUI[MD-refresh]: change cr-checkbox size to match paper-checkbox

Bug: 842818
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I291bc06e83d0976bb604e7707ae36b2264ebfd51
Reviewed-on: https://chromium-review.googlesource.com/1058069Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Scott Chen <scottchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558520}

ui/webui/resources/cr_elements/cr_checkbox/cr_checkbox.html

@@ -64,9 +64,9 @@ List of customizable styles:
         border-width: 0 2px 2px 0;
         content: '';
         display: block;
-        height: 70%;
+        height: 73%;
         transform: scale(0) rotate(45deg);
-        transform-origin: 100% 85%;
+        transform-origin: 118% 81%;
         width: 36%;
       }