Remove JavaScript const/let/lambda presubmit check for iOS9.

iOS9 is not supported by Chrome iOS and iGSA anymore, the presubmit check
for risky ES6 grammar(const/let/lambda) can be removed now.

Change-Id: I5a35d54097dbd215393aaba78868107befdc93b6
Reviewed-on: https://chromium-review.googlesource.com/c/1329249Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Yi Su <mrsuyi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606867}

PRESUBMIT.py

@@ -2717,70 +2717,6 @@ def _CheckNoDeprecatedJs(input_api, output_api):
   return results
 
 
-def _CheckForRiskyJsArrowFunction(line_number, line):
-  if ' => ' in line:
-    return "line %d, is using an => (arrow) function\n %s\n" % (
-        line_number, line)
-  return ''
-
-
-def _CheckForRiskyJsConstLet(input_api, line_number, line):
-  if input_api.re.match('^\s*(const|let)\s', line):
-    return "line %d, is using const/let keyword\n %s\n" % (
-        line_number, line)
-  return ''
-
-
-def _CheckForRiskyJsFeatures(input_api, output_api):
-  maybe_ios_js = [r"^(ios|components|ui\/webui\/resources)\/.+\.js$"]
-  # 'ui/webui/resources/cr_components are not allowed on ios'
-  not_ios_filter = (r".*ui\/webui\/resources\/cr_components.*", )
-  file_filter = lambda f: input_api.FilterSourceFile(f, white_list=maybe_ios_js,
-                                                     black_list=not_ios_filter)
-  results = []
-  for f in input_api.AffectedFiles(file_filter=file_filter):
-    arrow_error_lines = []
-    const_let_error_lines = []
-    for lnum, line in f.ChangedContents():
-      arrow_error_lines += filter(None, [
-        _CheckForRiskyJsArrowFunction(lnum, line),
-      ])
-
-      const_let_error_lines += filter(None, [
-        _CheckForRiskyJsConstLet(input_api, lnum, line),
-      ])
-
-    if arrow_error_lines:
-      arrow_error_lines = map(
-          lambda e: "%s:%s" % (f.LocalPath(), e), arrow_error_lines)
-      results.append(
-          output_api.PresubmitPromptWarning('\n'.join(arrow_error_lines + [
-"""
-Use of => (arrow) operator detected in:
-%s
-Please ensure your code does not run on iOS9 (=> (arrow) does not work there).
-https://chromium.googlesource.com/chromium/src/+/master/styleguide/web/es6.md#Arrow-Functions
-""" % f.LocalPath()
-          ])))
-
-    if const_let_error_lines:
-      const_let_error_lines = map(
-          lambda e: "%s:%s" % (f.LocalPath(), e), const_let_error_lines)
-      results.append(
-          output_api.PresubmitPromptWarning('\n'.join(const_let_error_lines + [
-"""
-Use of const/let keywords detected in:
-%s
-Please ensure your code does not run on iOS9 because const/let is not fully
-supported.
-https://chromium.googlesource.com/chromium/src/+/master/styleguide/web/es6.md#let-Block_Scoped-Variables
-https://chromium.googlesource.com/chromium/src/+/master/styleguide/web/es6.md#const-Block_Scoped-Constants
-""" % f.LocalPath()
-          ])))
-
-  return results
-
-
 def _CheckForRelativeIncludes(input_api, output_api):
   # Need to set the sys.path so PRESUBMIT_test.py runs properly
   import sys
@@ -3119,7 +3055,6 @@ def _CommonChecks(input_api, output_api):
   results.extend(_CheckJavaStyle(input_api, output_api))
   results.extend(_CheckIpcOwners(input_api, output_api))
   results.extend(_CheckUselessForwardDeclarations(input_api, output_api))
-  results.extend(_CheckForRiskyJsFeatures(input_api, output_api))
   results.extend(_CheckForRelativeIncludes(input_api, output_api))
   results.extend(_CheckWATCHLISTS(input_api, output_api))
   results.extend(input_api.RunTests(

PRESUBMIT_test.py

@@ -1391,54 +1391,6 @@ class ForwardDeclarationTest(unittest.TestCase):
     self.assertEqual(4, len(warnings))
 
 
-class RiskyJsTest(unittest.TestCase):
-  def testArrowWarnInIos9Code(self):
-    mock_input_api = MockInputApi()
-    mock_output_api = MockOutputApi()
-
-    mock_input_api.files = [
-      MockAffectedFile('components/blah.js', ["shouldn't use => here"]),
-    ]
-    warnings = PRESUBMIT._CheckForRiskyJsFeatures(
-        mock_input_api, mock_output_api)
-    self.assertEqual(1, len(warnings))
-
-    mock_input_api.files = [
-      MockAffectedFile('ios/blee.js', ['might => break folks']),
-    ]
-    warnings = PRESUBMIT._CheckForRiskyJsFeatures(
-        mock_input_api, mock_output_api)
-    self.assertEqual(1, len(warnings))
-
-    mock_input_api.files = [
-      MockAffectedFile('ui/webui/resources/blarg.js', ['on => iOS9']),
-    ]
-    warnings = PRESUBMIT._CheckForRiskyJsFeatures(
-        mock_input_api, mock_output_api)
-    self.assertEqual(1, len(warnings))
-
-  def testArrowsAllowedInChromeCode(self):
-    mock_input_api = MockInputApi()
-    mock_input_api.files = [
-      MockAffectedFile('chrome/browser/resources/blah.js', 'arrow => OK here'),
-    ]
-    warnings = PRESUBMIT._CheckForRiskyJsFeatures(
-        mock_input_api, MockOutputApi())
-    self.assertEqual(0, len(warnings))
-
-  def testConstLetWarningIos9Code(self):
-    mock_input_api = MockInputApi()
-    mock_output_api = MockOutputApi()
-
-    mock_input_api.files = [
-      MockAffectedFile('components/blah.js', [" const foo = 'bar';"]),
-      MockAffectedFile('ui/webui/resources/blah.js', [" let foo = 3;"]),
-    ]
-    warnings = PRESUBMIT._CheckForRiskyJsFeatures(
-        mock_input_api, mock_output_api)
-    self.assertEqual(2, len(warnings))
-
-
 class RelativeIncludesTest(unittest.TestCase):
   def testThirdPartyNotWebKitIgnored(self):
     mock_input_api = MockInputApi()