Clean up browser_resources.grd:...

chrome/browser/resources/ntp/most_visited.css

 /* Most Visited */
 
 #most-visited {
   position: relative;
   padding: 0;
   height: 366px;
   margin-top: -10px;
   -webkit-user-select: none;
 }
 
@@ skipping 102 matching lines @@
 
 .edit-bar > .pin,
 .edit-bar > .remove {
   width: 16px;
   height: 16px;
   cursor: pointer;
   background-image: no-repeat 50% 50%;
 }
 
 .edit-bar > .pin {
-  background-image: url(chrome://theme/IDR_NEWTAB_PIN_OFF);
+  background-image: url('ntp_pin_off.png');
 }
 
 .edit-bar > .pin:hover {
-  background-image: url(chrome://theme/IDR_NEWTAB_PIN_OFF_H);
+  background-image: url('ntp_pin_off_h.png');
 }
 
 .edit-bar > .pin:active {
-  background-image: url(chrome://theme/IDR_NEWTAB_PIN_OFF_P);
+  background-image: url('ntp_pin_off_p.png');
 }
 
 .pinned .edit-bar > .pin {
-  background-image: url(chrome://theme/IDR_NEWTAB_PIN_ON);
+  background-image: url('ntp_pin_on.png');
 }
 
 .pinned .edit-bar > .pin:hover {
-  background-image: url(chrome://theme/IDR_NEWTAB_PIN_ON_H);
+  background-image: url(ntp_pin_on_h.png');
 }
 
 .pinned .edit-bar > .pin:active {
-  background-image: url(chrome://theme/IDR_NEWTAB_PIN_ON_P);
+  background-image: url(ntp_pin_on_p.png');
 }
 
 .edit-bar > .remove {
-  background-image: url(chrome://theme/IDR_NEWTAB_CLOSE);
+  background-image: url('ntp_close.png');
 }
 
 .edit-bar > .remove:hover {
-  background-image: url(chrome://theme/IDR_NEWTAB_CLOSE_H);
+  background-image: url('ntp_close_h.png');
 }
 
 .edit-bar > .remove:active {
-  background-image: url(chrome://theme/IDR_NEWTAB_CLOSE_P);
+  background-image: url('ntp_close_p.png');
 }
 
 .thumbnail-container > .title > div {
   white-space: nowrap;
   overflow: hidden;
   text-overflow: ellipsis;
   background: no-repeat 0 50%;
   background-size: 16px;
   padding-left: 20px; /* we cannot use padding start here because even if we set
                          the direction we always want the icon on the same side
@@ skipping 85 matching lines @@
   }
 
   .thumbnail-container > .title {
     height: auto;
   }
 
   .thumbnail-wrapper {
     background-size: 150px 93px;
   }
 }