Convert Schedule to Chrome Timing format so it can be nicely visualized

[eruffaldi]

Check chrome://tracing
and https://chromedevtools.github.io/timeline-viewer/

https://github.com/tensorflow/tensorflow/blob/master/tensorflow/python/client/timeline.py

Args:
ph: The type of event - usually a single character.
category: The event category as a string.
name: The event name as a string.
pid: Identifier of the process generating this event as an integer.
tid: Identifier of the thread generating this event as an integer.
timestamp: The timestamp of this event as a long integer.

{
    "traceEvents": [
        {
            "ph": "M",
            "args": {
                "name": "Allocators"
            },
            "pid": 0,
            "name": "process_name"
        },
...
        {
            "name": "NoOp",
            "args": {
                "name": "_SOURCE",
                "op": "NoOp"
            },
            "pid": 1,
            "ts": 1521270814001434,
            "cat": "Op",
            "tid": 0,
            "ph": "X",
            "dur": 21
        },
]
}