DevTools: Add snapshot command log on the frontend.

Source/devtools/front_end/sdk/PaintProfiler.js

Index: Source/devtools/front_end/sdk/PaintProfiler.js
diff --git a/Source/devtools/front_end/sdk/PaintProfiler.js b/Source/devtools/front_end/sdk/PaintProfiler.js
index 46ad15ecd3843b1893835d8b21c359a8d5e0a41f..6735348fb33f091af49bfba4e5edd80f8e99f968 100644
--- a/Source/devtools/front_end/sdk/PaintProfiler.js
+++ b/Source/devtools/front_end/sdk/PaintProfiler.js
@@ -61,5 +61,16 @@ WebInspector.PaintProfilerSnapshot.prototype = {
     {
         var wrappedCallback = InspectorBackend.wrapClientCallback(callback, "LayerTreeAgent.profileSnapshot(): ");
         LayerTreeAgent.profileSnapshot(this._id, 5, 1, wrappedCallback);
+    },
+
+    /**
+     * @param {?number} firstStep
+     * @param {?number} lastStep
+     * @param {function(!Array.<!Object>=)} callback
+     */
+    commandLog: function(firstStep, lastStep, callback)
+    {
+        var wrappedCallback = InspectorBackend.wrapClientCallback(callback, "LayerTreeAgent.snapshotCommandLog(): ");
+        LayerTreeAgent.snapshotCommandLog(this._id, firstStep || undefined, lastStep || undefined, wrappedCallback);
     }
 };