Support merged Dart-JS callstacks

Source/devtools/protocol.json

 {
     "version": { "major": "1", "minor": "1" },
     "domains": [{
         "domain": "Inspector",
         "hidden": true,
         "types": [],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables inspector domain notifications."
@@ skipping 2944 matching lines @@
             },
             {
                 "id": "CallFrame",
                 "type": "object",
                 "properties": [
                     { "name": "callFrameId", "$ref": "CallFrameId", "description": "Call frame identifier. This identifier is only valid while the virtual machine is paused." },
                     { "name": "functionName", "type": "string", "description": "Name of the JavaScript function called on this call frame." },
                     { "name": "location", "$ref": "Location", "description": "Location in the source code." },
                     { "name": "scopeChain", "type": "array", "items": { "$ref": "Scope" }, "description": "Scope chain for this call frame." },
                     { "name": "this", "$ref": "Runtime.RemoteObject", "description": "<code>this</code> object for this call frame." },
-                    { "name": "returnValue", "$ref": "Runtime.RemoteObject", "optional": true, "hidden": true, "description": "The value being returned, if the function is at return point." }
+                    { "name": "returnValue", "$ref": "Runtime.RemoteObject", "optional": true, "hidden": true, "description": "The value being returned, if the function is at return point." },
+                    { "name": "timestamp", "type": "number", "optional": true, "description": "Relative ordering of call frames" }
                 ],
                 "description": "JavaScript call frame. Array of call frames form the call stack."
             },
             {
                 "id": "StackTrace",
                 "type": "object",
                 "properties": [
                     { "name": "callFrames", "type": "array", "items": { "$ref": "CallFrame" }, "description": "Call frames of the stack trace." },
                     { "name": "description", "type": "string", "optional": true, "description": "String label of this stack trace. For async traces this may be a name of the function that initiated the async call." },
                     { "name": "asyncStackTrace", "$ref": "StackTrace", "optional": true, "description": "Async stack trace, if any." }
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             {
                 "name": "dataAvailable",
                 "parameters": [
                     {"name": "value", "type": "array", "items": { "$ref": "PowerEvent" }, "description": "List of power events." }
                 ],
                 "handlers": ["browser", "frontend"]
             }
         ]
     }]
 }