add diff viewer website

experimental/skpdiff/diff_viewer.js

+function DiffViewController($scope) {
+    $scope.differs = [
+        {
+            "title": "Different Pixels"
+        },
+        {
+            "title": "Perceptual Difference"
+        }
+    ];
+    $scope.sortIndex = 1;
+    $scope.records = SkPDiffRecords.records;
+    $scope.highlight = function(differName) {
+        console.debug(differName);
+    }
+    $scope.setSortIndex = function(a) {
+        $scope.sortIndex = a;
+    }
+    $scope.sortingDiffer = function(a) {
+        console.debug($scope.sortIndex);
+        return a.diffs[$scope.sortIndex].result;
+    }
+}