[xray] Implement timeline and profiling API. (#2306)

* Add profile table and store profiling information there.

* Code for dumping timeline.

* Improve color scheme.

* Push timeline events on driver only for raylet.

* Improvements to profiling and timeline visualization

* Some linting

* Small fix.

* Linting

* Propagate node IP address through profiling events.

* Fix test.

* object_id.hex() should return byte string in python 2.

* Include gcs.fbs in node_manager.fbs.

* Remove flatbuffer definition duplication.

* Decode to unicode in Python 3 and bytes in Python 2.

* Minor

* Submit profile events in a batch. Revert some CMake changes.

* Fix

* Workaround test failure.

* Fix linting

* Linting

* Don't return anything from chrome_tracing_dump when filename is provided.

* Remove some redundancy from profile table.

* Linting

* Move TODOs out of docstring.

* Minor

python/ray/scripts/scripts.py

@@ -10,6 +10,7 @@ import subprocess
 import ray.services as services
 from ray.autoscaler.commands import (create_or_update_cluster,
                                      teardown_cluster, get_head_node_ip)
+import ray.utils
 
 
 def check_no_existing_redis_clients(node_ip_address, redis_client):
@@ -31,7 +32,7 @@ def check_no_existing_redis_clients(node_ip_address, redis_client):
         if deleted:
             continue
 
-        if info[b"node_ip_address"].decode("ascii") == node_ip_address:
+        if ray.utils.decode(info[b"node_ip_address"]) == node_ip_address:
             raise Exception("This Redis instance is already connected to "
                             "clients with this IP address.")