Prevent icons in the detail view from getting outside the file name column.

.detail-checkmark creates a new containing block by position:absolute so that it is always clickable, but the thumbnail icons should not do that.

BUG=630236

Review-Url: https://codereview.chromium.org/2166353002
Cr-Commit-Position: refs/heads/master@{#407103}

ui/file_manager/file_manager/foreground/css/file_manager.css

@@ -1804,7 +1804,6 @@ body.check-select #list-container li[selected] .detail-checkmark {
 #list-container list li .detail-thumbnail {
   height: 28px;
   overflow: hidden;
-  position: absolute;
   width: 28px;
 }
 
@@ -1816,7 +1815,6 @@ body.check-select #list-container li[selected] .detail-checkmark {
   border-radius: 14px;
   height: 100%;
   opacity: 1;
-  position: absolute;
   width: 100%;
 }