Clean up browser_resources.grd:...

chrome/browser/resources/new_new_tab.css

 html {
   /* This is needed because of chrome://theme/css/new_tab.css */
   height: 100%;
 }
 
 body {
   margin: 0;
   height: 100%;
   overflow: auto;
   -webkit-user-select: none;
@@ skipping 138 matching lines @@
   padding-right: 18px;
   padding-left: 2px;
   text-align: right;
 }
 
 .window {
   overflow: visible; /* We use visible so that the menu can be a child and shown
                         on :hover. To get this to work we have to set visibility
                         to visible which unfortunately breaks the ellipsis for t
                         he window items */
-  background-image: url(chrome://theme/IDR_NEWTAB_CLOSED_WINDOW);
+  background-image: url('ntp/closed_window.png');
 }
 
 .window-menu {
   position: absolute;
   display: none;
   border: 1px solid #999;
   -webkit-box-shadow: 2px 2px 3px hsla(0, 0%, 0%, .3);
   color: black;
   background-color: white;
   left: 0;
@@ skipping 163 matching lines @@
   background-repeat: no-repeat;
   width: 14px;
 }
 
 html[dir=rtl] #option-menu > [command=show]:before,
 html[dir=rtl] #option-menu > [command=hide]:before {
   background-position-x: 100%;
 }
 
 #option-menu > [command=hide]:before {
-  background-image: url(chrome://theme/IDR_NEWTAB_CHECKBOX_BLACK);
+  background-image: url('ntp/checkbox_black.png');
 }
 
 #option-menu > [selected][command=hide]:active:before {
-  background-image: url(chrome://theme/IDR_NEWTAB_CHECKBOX_WHITE);
+  background-image: url('ntp/checkbox_white.png');
 }
 
 #attribution {
   margin: 10px 0;
 }
 
 .sync-button {
   font-size: inherit;
   padding: 0;
   margin: 0;
@@ skipping 131 matching lines @@
 #footer hr {
   border: 0;
   display: inline;
   margin: 0;
   padding: 0;
 }
 
 #footer hr:after {
   content: "|";
 }