add ui for mutli-rebaselining

tools/skpdiff/viewer_style.css

 body, img, div {
     font-family: Verdana;
     margin: 0;
     padding: 0;
 }
 
 table {
     width:100%;
     border-collapse: collapse;
     border-spacing: 0;
     padding: 8px;
 }
 
 td {
     border-top: 1px solid #DDD;
     padding: 8px;
 }
 thead > tr > td {
     border: none;
 }
 
+button {
+    font-family: Verdana;
+    font-weight: 900;
+}
+
+input[type="checkbox"] {
+    -webkit-appearance: none;
+    -moz-appearance: none;
+    width: 20px;
+    height:20px;
+    padding: 2px;
+    background: #EEE;
+    border-radius: 2px;
+    box-shadow: inset 0 0 8px -2px black;
+}
+
+input[type="checkbox"]:checked {
+    background: #a9db80;
+    background:  -webkit-linear-gradient(top, #00b7ea 0%,#009ec3 100%);
+}
+
+input[type="checkbox"]:active {
+    background: #a9db80;
+    background: -webkit-linear-gradient(top, #009ec3 0%,#00b7ea 100%);
+}
+
+input[type="checkbox"].lastselected {
+    padding: 0;
+    border: 2px solid #009ec3;
+    box-shadow: inset 0 0 8px -2px black, 0 0 6px black;
+}
+
+.commit {
+    position: absolute;
+    top: 8px;
+    right: 8px;
+}
+
+.commit > button {
+    border: 1px solid #00687F;
+    border-radius: 4px;
+    padding: 8px;
+    color: white;
+    text-shadow: 0 0 4px black;
+    box-shadow: 0 0 8px black;
+    background: #a9db80;
+    background: -webkit-linear-gradient(top, #a9db80 0%,#96c56f 100%);
+}
+
+.commit > button:active {
+    background: #96c56f;
+    background: -webkit-linear-gradient(top, #96c56f 0%,#a9db80 100%);
+}
+
 .gm-image {
     border: 1px dotted black;
 }
 
 .gm-image:hover {
     border: 1px dashed black;
 }
 
+.selected {
+    background: #ffff88;
+}
+
 .left-image {
     float: right;
 }
 
 .right-image {
     text-align: right;
 }
 
 .success-flash {
     -webkit-animation-duration: 0.5s;
@@ skipping 21 matching lines @@
     }
 
     to {
         background-color: #FFF
     }
 }
 
 .result {
     padding: 8px;
     cursor: default;
-    opacity: 0.7;
+    -webkit-filter: grayscale(30%)
 }
 
 .result:hover {
     border: 2px dotted #DDD;
     padding: 6px;
-    opacity: 1.0;
+    -webkit-filter: grayscale(0)
 }
 
 .result-0 {
     background-color: #268bd2;
 }
 
 .result-1 {
     background-color: #d33682;
 }
 
@@ skipping 13 matching lines @@
     background-color: #dc322f;
 }
 
 .result-6 {
     background-color: #2aa198;
 }
 
 .result-7 {
     background-color: #859900;
 }