[blink] Add --enable-tracing flag to layout test runner.

Add a flag to enable capturing a trace file for layout tests, similar
to how browser tests do this:

run_web_tests.py --enable-tracing=CATEGORIES

The implementation passed the following flags to the driver:
--trace-startup
--trace-startup-duration=0
--trace-startup-file

R=robertma@chromium.org

Change-Id: I2f145936f567986219928108eba89c8c60f734a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2202807
Commit-Queue: Alexander Timin <altimin@chromium.org>
Reviewed-by: Robert Ma <robertma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#769473}

third_party/blink/tools/blinkpy/web_tests/controllers/web_test_runner.py

@@ -349,10 +349,16 @@ class Worker(object):
         if self._driver:
             # When tracing we need to go through the standard shutdown path to
             # ensure that the trace is recorded properly.
-            if any(i in ['--trace-startup', '--trace-shutdown']
-                   for i in self._options.additional_driver_flag):
+            tracing_enabled = self._port.get_option(
+                'enable_tracing') is not None or any(
+                    flag.startswith(tracing_command) for tracing_command in
+                    ['--trace-startup', '--trace-shutdown']
+                    for flag in self._options.additional_driver_flag)
+
+            if tracing_enabled:
                 _log.debug('%s waiting %d seconds for %s driver to shutdown',
-                           self._name, self._port.driver_stop_timeout(), label)
+                           self._name, self._port.driver_stop_timeout(),
+                           self._name)
                 self._driver.stop(
                     timeout_secs=self._port.driver_stop_timeout())
                 return

third_party/blink/tools/blinkpy/web_tests/port/base.py

@@ -31,6 +31,7 @@ The Port classes encapsulate Port-specific (platform-specific) behavior
 in the web test infrastructure.
 """
 
+import time
 import collections
 import itertools
 import json
@@ -1195,7 +1196,20 @@ class Port(object):
 
     @memoized
     def args_for_test(self, test_name):
-        return self._lookup_virtual_test_args(test_name)
+        args = self._lookup_virtual_test_args(test_name)
+        tracing_categories = self.get_option('enable_tracing')
+        if tracing_categories:
+            args.append('--trace-startup=' + tracing_categories)
+            # Do not finish the trace until the test is finished.
+            args.append('--trace-startup-duration=0')
+            # Append the current time to the output file name to ensure that
+            # the subsequent repetitions of the test do not overwrite older
+            # trace files.
+            current_time = time.strftime("%Y-%m-%d-%H-%M-%S")
+            file_name = 'trace_layout_test_' + test_name.replace(
+                '/', '_').replace('.', '_') + '_' + current_time + '.json'
+            args.append('--trace-startup-file=' + file_name)
+        return args
 
     @memoized
     def name_for_test(self, test_name):

third_party/blink/tools/blinkpy/web_tests/port/base_unittest.py

@@ -29,6 +29,7 @@
 import json
 import optparse
 import unittest
+import mock
 
 from blinkpy.common.path_finder import RELATIVE_WEB_TESTS
 from blinkpy.common.system.executive_mock import MockExecutive
@@ -1664,6 +1665,18 @@ class PortTest(LoggingTestCase):
                       port.additional_driver_flags())
 
 
+    def test_enable_tracing(self):
+        options, _ = optparse.OptionParser().parse_args([])
+        options.enable_tracing = '*,-blink'
+        port = self.make_port(with_tests=True, options=options)
+        with mock.patch('time.strftime', return_value='TIME'):
+            self.assertEqual([
+                '--trace-startup=*,-blink',
+                '--trace-startup-duration=0',
+                '--trace-startup-file=trace_layout_test_non_virtual_TIME.json',
+            ], port.args_for_test('non/virtual'))
+
+
 class NaturalCompareTest(unittest.TestCase):
     def setUp(self):
         self._port = TestPort(MockSystemHost())

third_party/blink/tools/blinkpy/web_tests/run_web_tests.py

@@ -295,11 +295,10 @@ def parse_args(args):
                 dest='build',
                 action='store_false',
                 help="Don't check to see if the build is up to date."),
-            optparse.make_option(
-                '--child-processes',
-                '--jobs',
-                '-j',
-                help='Number of drivers to run in parallel.'),
+            optparse.make_option('--child-processes',
+                                 '--jobs',
+                                 '-j',
+                                 help='Number of drivers to run in parallel.'),
             optparse.make_option(
                 '--disable-breakpad',
                 action='store_true',
@@ -316,6 +315,12 @@ def parse_args(args):
                 '--enable-sanitizer',
                 action='store_true',
                 help='Only alert on sanitizer-related errors and crashes'),
+            optparse.make_option(
+                '--enable-tracing',
+                type='string',
+                help='Capture and write a trace file with the specied '
+                'categories for each test. Passes appropriate --trace-startup '
+                'flags to the driver.'),
             optparse.make_option(
                 '--exit-after-n-crashes-or-timeouts',
                 type='int',
@@ -386,10 +391,9 @@ def parse_args(args):
                  "'random' == pseudo-random order (default). Seed can be specified "
                  'via --seed, otherwise it will default to the current unix timestamp. '
                  "'natural' == use the natural order")),
-            optparse.make_option(
-                '--profile',
-                action='store_true',
-                help='Output per-test profile information.'),
+            optparse.make_option('--profile',
+                                 action='store_true',
+                                 help='Output per-test profile information.'),
             optparse.make_option(
                 '--profiler',
                 action='store',
@@ -515,8 +519,8 @@ def parse_args(args):
                 help='A colon-separated list of tests to run. Wildcards are '
                 'NOT supported. It is the same as listing the tests as '
                 'positional arguments.'),
-            optparse.make_option(
-                '--time-out-ms', help='Set the timeout for each test'),
+            optparse.make_option('--time-out-ms',
+                                 help='Set the timeout for each test'),
             optparse.make_option(
                 '--wrapper',
                 help=
@@ -524,11 +528,10 @@ def parse_args(args):
                  'is split on whitespace before running. (Example: --wrapper="valgrind '
                  '--smc-check=all")')),
             # FIXME: Display the default number of child processes that will run.
-            optparse.make_option(
-                '-f',
-                '--fully-parallel',
-                action='store_true',
-                help='run all tests in parallel'),
+            optparse.make_option('-f',
+                                 '--fully-parallel',
+                                 action='store_true',
+                                 help='run all tests in parallel'),
             optparse.make_option(
                 '--virtual-parallel',
                 action='store_true',