[devtools] Add DOMSnapshot domain for dom+layout+style snapshots.

third_party/WebKit/LayoutTests/inspector-protocol/css/css-getLayoutTreeNodes.html

Index: third_party/WebKit/LayoutTests/inspector-protocol/css/css-getLayoutTreeNodes.html
diff --git a/third_party/WebKit/LayoutTests/inspector-protocol/css/css-getLayoutTreeNodes.html b/third_party/WebKit/LayoutTests/inspector-protocol/css/css-getLayoutTreeNodes.html
index 43ea5445abe3b8cf023e430d89d0c2fe6b3333ab..21348521e9f9631e0da2486323c901e0f4587256 100644
--- a/third_party/WebKit/LayoutTests/inspector-protocol/css/css-getLayoutTreeNodes.html
+++ b/third_party/WebKit/LayoutTests/inspector-protocol/css/css-getLayoutTreeNodes.html
@@ -22,26 +22,9 @@ function test()
     function onLayoutTreeNodes(response)
     {
         InspectorTest.log("\nLayoutTreeNodes result:");
-        canonicalizeBackendNodeIds(response);
         InspectorTest.log(JSON.stringify(response, null, 2));
         InspectorTest.completeTest();
     }
-
-    // While unique the backendNodeId IDs are not stable cross platform, so we canonicalize them.
-    var nextId = 1;
-    var nodeMap = {}; 
-    function canonicalizeBackendNodeIds(node) {
-        if (node.hasOwnProperty('backendNodeId')) {
-            if (!nodeMap.hasOwnProperty(node.backendNodeId)) {
-                nodeMap[node.backendNodeId] = nextId++;
-            }
-            node.backendNodeId = nodeMap[node.backendNodeId];
-        }
-        for (var property in node) {
-            if (!node.hasOwnProperty(property) || typeof node[property] === 'object')
-                canonicalizeBackendNodeIds(node[property]);
-        }
-    }
 }
 
 </script>