add ui for mutli-rebaselining

tools/skpdiff/viewer_style.css

Index: tools/skpdiff/viewer_style.css
diff --git a/tools/skpdiff/viewer_style.css b/tools/skpdiff/viewer_style.css
index 81b4f906c99b31e333c2a3bf4523d40bca2a51a8..e172667061296b00a6f94893a1c0a23be968381c 100644
--- a/tools/skpdiff/viewer_style.css
+++ b/tools/skpdiff/viewer_style.css
@@ -19,6 +19,60 @@ 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;
 }
@@ -27,6 +81,10 @@ thead > tr > td {
     border: 1px dashed black;
 }
 
+.selected {
+    background: #ffff88;
+}
+
 .left-image {
     float: right;
 }
@@ -68,13 +126,13 @@ thead > tr > td {
 .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 {