[NTP] Increase edit menu size to 20px

Screenshot: https://screenshot.googleplex.com/53hB2LzA1Mj.png

Bug: 867587
Change-Id: I7589715970a4a2f3c3a53805dadfe3026a21bb7a
Reviewed-on: https://chromium-review.googlesource.com/1156001Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Commit-Queue: Kristi Park <kristipark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579633}

chrome/browser/resources/local_ntp/most_visited_single.css

@@ -4,6 +4,7 @@
 
 html {
   /* Material Design constants */
+  --md-edit-menu-size: 20px;
   --md-fallback-letter-size: 21px;
   --md-favicon-size: 24px;
   --md-icon-margin-bottom: 16px;
@@ -542,9 +543,16 @@ body.dark-theme .md-tile:active .md-menu::after {
   width: var(--md-menu-size);
 }
 
+.md-edit-menu {
+  height: var(--md-edit-menu-size);
+  width: var(--md-edit-menu-size);
+}
+
 .md-edit-menu::after {
-  --mask-width: var(--md-menu-size);
+  --mask-width: var(--md-edit-menu-size);
   -webkit-mask-image: url(chrome-search://most-visited/edit_menu.svg);
+  height: var(--md-edit-menu-size);
+  width: var(--md-edit-menu-size);
 }
 
 body.dark-theme .md-menu::after {