Revert "Set limit for field trial parameters length."

This reverts commit 1547c775.

Reason for revert: Causes "No module named fieldtrial_util" error when running "git cl try".

Original change's description:
> Set limit for field trial parameters length.
> 
> Windows has a limit of 32767 on a command line. When testing with field
> trails, the command to launch chrome.exe may exceed the limit if there're
> too many field trial configs passed as parameters. This was causing
> the chrome perf waterfall to completely fail on Windows.
> 
> This CL added a presubmit check to see whether the configs under Windows
> will exceed the limit of 31000.
> 
> Bug: chromium:1045530
> Change-Id: I9d181783f1bdad58eeba802583c052bfd0321c6f
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2021468
> Commit-Queue: Wenbin Zhang <wenbinzhang@google.com>
> Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
> Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#735981}

TBR=asvitkine@chromium.org,crouleau@chromium.org,wenbinzhang@google.com

Change-Id: I42f928aa6bc87b1f5696f8bda50d6d307d53ff7c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:1045530
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2025830Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736026}

testing/variations/PRESUBMIT.py

@@ -10,10 +10,6 @@ for more details on the presubmit API built into depot_tools.
 import copy
 import json
 import sys
-import os
-
-sys.path.insert(0, os.path.abspath('../../tools/variations'))
-import fieldtrial_util
 
 from collections import OrderedDict
 
@@ -22,16 +18,6 @@ VALID_EXPERIMENT_KEYS = [
     '//0', '//1', '//2', '//3', '//4', '//5', '//6', '//7', '//8', '//9'
 ]
 
-FIELDTRIAL_CONFIG_FILE_NAME = 'fieldtrial_testing_config.json'
-
-FIELDTRIAL_CONFIG_TOO_LONG_ERROR_MSG = \
-  "Contents of %s result in command-line flags that exceed Windows' 32767 "\
-  "character limit. To add a new entry, please remove existing obsolete "\
-  "entries. To check if an entry is obsolete, do a code search for its "\
-  "'enable_features' and 'disable_features' strings and verify there are "\
-  "no results other than the files related to the testing config. "\
-  "See crbug.com/1045530 for more details." % FIELDTRIAL_CONFIG_FILE_NAME
-
 
 def PrettyPrint(contents):
   """Pretty prints a fieldtrial configuration.
@@ -120,9 +106,6 @@ def ValidateData(json_data, file_path, message_type):
     return _CreateMalformedConfigMessage(message_type, file_path,
                                          message_format, *args)
 
-  if not _IsFieldTrialSizeBelowLimitOnWindows(file_path):
-    return [message_type(FIELDTRIAL_CONFIG_TOO_LONG_ERROR_MSG)]
-
   if not isinstance(json_data, dict):
     return _CreateMessage('Expecting dict')
   for (study, experiment_configs) in json_data.iteritems():
@@ -245,45 +228,15 @@ def CheckPretty(contents, file_path, message_type):
   return []
 
 
-def _IsFieldTrialSizeBelowLimitOnWindows(file_path):
-  """Checks whether the fieldtrial parameters exceeded the Windows cmd limit.
-
-  When launching chrome, the fieldtrial related parameters take more than
-  30,000 characters. Windows has a limit of 32767 characters on command
-  line and thus it raises parameter error when the parameters are too long.
-  Before we have a valid fix, we need to limit the number of fieldtrias in
-  fieldtrial_testing_config.json to 31,000, from the fact that the
-  non-fieldtrial parameters take roughly 1450 characters.
-  See crbug.com/1045530 for more details.
-
-  Args:
-    file_path: the absolute path to the json file with the fieldtrial configs.
-  """
-  args = fieldtrial_util.GenerateArgs(file_path, 'windows')
-  total_length = 0
-  for arg in args:
-    total_length += len(arg)
-  return total_length < 31000
-
-
 def CommonChecks(input_api, output_api):
   affected_files = input_api.AffectedFiles(
       include_deletes=False,
       file_filter=lambda x: x.LocalPath().endswith('.json'))
   for f in affected_files:
-    if not f.LocalPath().endswith(FIELDTRIAL_CONFIG_FILE_NAME):
-      return [
-          output_api.PresubmitError(
-              '%s is the only json file expected in this folder. If new jsons '
-              'are added, please update the presubmit process with proper '
-              'validation. ' % FIELDTRIAL_CONFIG_FILE_NAME
-          )
-      ]
     contents = input_api.ReadFile(f)
     try:
       json_data = input_api.json.loads(contents)
-      result = ValidateData(
-          json_data, f.AbsoluteLocalPath(), output_api.PresubmitError)
+      result = ValidateData(json_data, f.LocalPath(), output_api.PresubmitError)
       if len(result):
         return result
       result = CheckPretty(contents, f.LocalPath(), output_api.PresubmitError)