Make all checkboxes uniformly darker.

chrome/browser/resources/file_manager/css/common.css

Index: chrome/browser/resources/file_manager/css/common.css
diff --git a/chrome/browser/resources/file_manager/css/common.css b/chrome/browser/resources/file_manager/css/common.css
index eac94a747bf72c2f7c00080e3ea6992bfab7d540..87824d48a70abd2d1a2f22ea0a5d7d3eefac840a 100644
--- a/chrome/browser/resources/file_manager/css/common.css
+++ b/chrome/browser/resources/file_manager/css/common.css
@@ -10,15 +10,23 @@ input.common[type='radio'] {
   -webkit-appearance: none;
   -webkit-border-radius: 1px;
   -webkit-box-sizing: border-box;
-  border: 1px solid #c6c6c6;
+  border: 1px solid #555;
   border-radius: 1px;
   box-sizing: border-box;
   cursor: default;
   height: 13px;
   margin: 0;
+  opacity: 0.4;
   width: 13px;
 }
 
+input.common[type='checkbox']:hover,
+input.common[type='checkbox']:checked,
+input.common[type='radio']:hover,
+input.common[type='radio']:checked {
+  opacity: 1;
+}
+
 input.common[type='checkbox'] {
   position: relative;
 }