[inspector] introduced stepIntoAsync for chained callbacks

src/inspector/js_protocol.json

 {
     "version": { "major": "1", "minor": "2" },
     "domains": [
     {
         "domain": "Schema",
         "description": "Provides information about the protocol schema.",
         "types": [
             {
                 "id": "Domain",
                 "type": "object",
@@ skipping 540 matching lines @@
             },
             {
                 "name": "stepOver",
                 "description": "Steps over the statement."
             },
             {
                 "name": "stepInto",
                 "description": "Steps into the function call."
             },
             {
+                "name": "stepIntoAsync",
+                "description": "Steps into the scheduled callback."
+            },
+            {
                 "name": "stepOut",
                 "description": "Steps out of the function call."
             },
             {
                 "name": "pause",
                 "description": "Stops on the next JavaScript statement."
             },
             {
                 "name": "resume",
                 "description": "Resumes JavaScript execution."
@@ skipping 148 matching lines @@
                 "parameters": [
                     { "name": "breakpointId", "$ref": "BreakpointId", "description": "Breakpoint unique identifier." },
                     { "name": "location", "$ref": "Location", "description": "Actual breakpoint location." }
                 ],
                 "description": "Fired when breakpoint is resolved to an actual script and location."
             },
             {
                 "name": "paused",
                 "parameters": [
                     { "name": "callFrames", "type": "array", "items": { "$ref": "CallFrame" }, "description": "Call stack the virtual machine stopped on." },
-                    { "name": "reason", "type": "string", "enum": [ "XHR", "DOM", "EventListener", "exception", "assert", "debugCommand", "promiseRejection", "OOM", "other" ], "description": "Pause reason." },
+                    { "name": "reason", "type": "string", "enum": [ "XHR", "DOM", "EventListener", "exception", "assert", "debugCommand", "promiseRejection", "OOM", "other", "callbackScheduled" ], "description": "Pause reason." },
                     { "name": "data", "type": "object", "optional": true, "description": "Object containing break-specific auxiliary properties." },
                     { "name": "hitBreakpoints", "type": "array", "optional": true, "items": { "type": "string" }, "description": "Hit breakpoints IDs" },
                     { "name": "asyncStackTrace", "$ref": "Runtime.StackTrace", "optional": true, "description": "Async stack trace, if any." }
                 ],
                 "description": "Fired when the virtual machine stopped on breakpoint or exception or any other stop criteria."
             },
             {
                 "name": "resumed",
                 "description": "Fired when the virtual machine resumed execution."
             }
@@ skipping 253 matching lines @@
             {
                 "name": "heapStatsUpdate",
                 "description": "If heap objects tracking has been started then backend may send update for one or more fragments",
                 "parameters": [
                     { "name": "statsUpdate", "type": "array", "items": { "type": "integer" }, "description": "An array of triplets. Each triplet describes a fragment. The first integer is the fragment index, the second integer is a total count of objects for the fragment, the third integer is a total size of the objects for the fragment."}
                 ]
             }
         ]
     }]
 }