Gallery: Enlarge the size of range inputs in Gallery.

To show the focus ring in the correct size, the CL enlarges the size of range
inputs in Gallery. Instead, the CL adds pseudo element to draw the range track
(a thin horizontal bar).

BUG=397062
TEST=manually

Review URL: https://codereview.chromium.org/419153002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@285535 0039d316-1c4b-4281-b951-d872f2087c98

ui/file_manager/gallery/css/gallery.css

@@ -883,9 +883,21 @@ input[type='checkbox']:checked {
 
 .gallery .edit-modal .range {
   -webkit-appearance: none !important;
-  height: 3px;
+  background: transparent;
+  height: 29px;
   margin-right: 10px;
-  margin-top: 1px;
+  position: relative;
+}
+
+.gallery .edit-modal .range::before {
+  background: #fff;
+  content: '';
+  display: block;
+  height: 3px;
+  left: 3px;
+  position: absolute;
+  right: 3px;
+  top: 13px;
 }
 
 .gallery .edit-modal .range::-webkit-slider-thumb {