Add plugin that profiles playbook tasks

Resubmission of https://github.com/ansible/ansible/pull/11270 to
correct v2 file location.

[Description and console output
demonstration](https://github.com/aioue/ansible-plugin-profile/blob/mast
er/README.md#features).

Provides per-task timing, ongoing playbook elapsed time and ordered
list of top 20 longest running tasks at end.

lib/ansible/plugins/callback/profile_tasks.py

@@ -0,0 +1,106 @@
+# (C) 2015, Tom Paine, <github@aioue.net>
+# (C) 2014, Jharrod LaFon, @JharrodLaFon
+# (C) 2012-2013, Michael DeHaan, <michael.dehaan@gmail.com>
+#
+# This file is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# File is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# See <http://www.gnu.org/licenses/> for a copy of the
+# GNU General Public License
+
+# Provides per-task timing, ongoing playbook elapsed time and
+# ordered list of top 20 longest running tasks at end
+
+import time
+
+from ansible.callbacks import display
+
+
+# define start time
+t0 = tn = time.time()
+
+
+def secondsToStr(t):
+    # http://bytes.com/topic/python/answers/635958-handy-short-cut-formatting-elapsed-time-floating-point-seconds
+    rediv = lambda ll, b: list(divmod(ll[0], b)) + ll[1:]
+    return "%d:%02d:%02d.%03d" % tuple(reduce(rediv, [[t * 1000, ], 1000, 60, 60]))
+
+
+def filled(msg, fchar="*"):
+    if len(msg) == 0:
+        width = 79
+    else:
+        msg = "%s " % msg
+        width = 79 - len(msg)
+    if width < 3:
+        width = 3
+    filler = fchar * width
+    return "%s%s " % (msg, filler)
+
+
+def timestamp(self):
+    if self.current is not None:
+        self.stats[self.current] = time.time() - self.stats[self.current]
+
+
+def tasktime():
+    global tn
+    time_current = time.strftime('%A %d %B %Y  %H:%M:%S %z')
+    time_elapsed = secondsToStr(time.time() - tn)
+    time_total_elapsed = secondsToStr(time.time() - t0)
+    display(filled('%s (%s)%s%s' % (time_current, time_elapsed, ' ' * 7, time_total_elapsed)))
+    tn = time.time()
+
+
+class CallbackModule(object):
+
+    def __init__(self):
+        self.stats = {}
+        self.current = None
+
+    def playbook_on_task_start(self, name, is_conditional):
+        """
+        Logs the start of each task
+        """
+        tasktime()
+        timestamp(self)
+
+        # Record the start time of the current task
+        self.current = name
+        self.stats[self.current] = time.time()
+
+    def playbook_on_setup(self):
+        tasktime()
+
+    def playbook_on_stats(self, stats):
+        tasktime()
+        display(filled("", fchar="="))
+
+        timestamp(self)
+
+        # Sort the tasks by their running time
+        results = sorted(
+            self.stats.items(),
+            key=lambda value: value[1],
+            reverse=True,
+        )
+
+        # Just keep the top 20
+        results = results[:20]
+
+        # Print the timings
+        for name, elapsed in results:
+            print(
+                "{0:-<70}{1:->9}".format(
+                    '{0} '.format(name),
+                    ' {0:.02f}s'.format(elapsed),
+                )
+            )
+        print ''