diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 8c75942ccf..bc4eaf2721 100755
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -580,7 +580,7 @@ def CheckGnGen(input_api, output_api):
   """
   with _AddToPath(input_api.os_path.join(
       input_api.PresubmitLocalPath(), 'tools_webrtc', 'presubmit_checks_lib')):
-    from gn_check import RunGnCheck
+    from build_helpers import RunGnCheck
   errors = RunGnCheck(FindSrcDirPath(input_api.PresubmitLocalPath()))[:5]
   if errors:
     return [output_api.PresubmitPromptWarning(
diff --git a/tools_webrtc/__init__.py b/tools_webrtc/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/tools_webrtc/clang_tidy.py b/tools_webrtc/clang_tidy.py
new file mode 100755
index 0000000000..49a9427f09
--- /dev/null
+++ b/tools_webrtc/clang_tidy.py
@@ -0,0 +1,96 @@
+#!/usr/bin/env python
+# Copyright (c) 2019 The WebRTC project authors. All Rights Reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS.  All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+
+"""Invoke clang-tidy tool.
+
+Usage: clang_tidy.py file.cc [clang-tidy-args...]
+
+Just a proof of concept!
+We use an embedded clang-tidy whose version doesn't match clang++.
+"""
+
+import argparse
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+#pylint: disable=relative-import
+from presubmit_checks_lib.build_helpers import GetClangTidyPath, \
+  GetCompilationCommand
+
+
+# We enable all checkers by default for investigation purpose.
+# This includes clang-analyzer-* checks.
+# Individual checkers can be disabled via command line options.
+# TODO(bugs.webrtc.com/10258): Select checkers relevant to webrtc guidelines.
+CHECKER_OPTION = '-checks=*'
+
+
+def Process(filepath, args):
+  # Build directory is needed to gather compilation flags.
+  # Create a temporary one (instead of reusing an existing one)
+  # to keep the CLI simple and unencumbered.
+  out_dir = tempfile.mkdtemp('clang_tidy')
+
+  try:
+    gn_args = []  # Use default build.
+    command = GetCompilationCommand(filepath, gn_args, out_dir)
+
+    # Remove warning flags. They aren't needed and they cause trouble
+    # when clang-tidy doesn't match most recent clang.
+    # Same battle for -f (e.g. -fcomplete-member-pointers).
+    command = [arg for arg in command if not (arg.startswith('-W') or
+                                              arg.startswith('-f'))]
+
+    # Path from build dir.
+    rel_path = os.path.relpath(os.path.abspath(filepath), out_dir)
+
+    # Replace clang++ by clang-tidy
+    command[0:1] = [GetClangTidyPath(),
+                    CHECKER_OPTION,
+                    rel_path] + args + ['--']  # Separator for clang flags.
+    print "Running: %s" % ' '.join(command)
+    # Run from build dir so that relative paths are correct.
+    p = subprocess.Popen(command, cwd=out_dir,
+                         stdout=sys.stdout, stderr=sys.stderr)
+    p.communicate()
+    return p.returncode
+  finally:
+    shutil.rmtree(out_dir, ignore_errors=True)
+
+
+def ValidateCC(filepath):
+  """We can only analyze .cc files. Provide explicit message about that."""
+  if filepath.endswith('.cc'):
+    return filepath
+  msg = ('%s not supported.\n'
+         'For now, we can only analyze translation units (.cc files).' %
+         filepath)
+  raise argparse.ArgumentTypeError(msg)
+
+
+def Main():
+  description = (
+    "Run clang-tidy on single cc file.\n"
+    "Use flags, defines and include paths as in default debug build.\n"
+    "WARNING, this is a POC version with rough edges.")
+  parser = argparse.ArgumentParser(description=description)
+  parser.add_argument('filepath',
+                      help='Specifies the path of the .cc file to analyze.',
+                      type=ValidateCC)
+  parser.add_argument('args',
+                      nargs=argparse.REMAINDER,
+                      help='Arguments passed to clang-tidy')
+  parsed_args = parser.parse_args()
+  return Process(parsed_args.filepath, parsed_args.args)
+
+
+if __name__ == '__main__':
+  sys.exit(Main())
diff --git a/tools_webrtc/presubmit_checks_lib/__init__.py b/tools_webrtc/presubmit_checks_lib/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/tools_webrtc/presubmit_checks_lib/build_helpers.py b/tools_webrtc/presubmit_checks_lib/build_helpers.py
new file mode 100644
index 0000000000..1ad59bfd49
--- /dev/null
+++ b/tools_webrtc/presubmit_checks_lib/build_helpers.py
@@ -0,0 +1,134 @@
+# Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS.  All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+
+"""This script helps to invoke gn and ninja
+which lie in depot_tools repository."""
+
+import json
+import os
+import re
+import shutil
+import subprocess
+import sys
+import tempfile
+
+
+def FindSrcDirPath():
+  """Returns the abs path to the src/ dir of the project."""
+  src_dir = os.path.dirname(os.path.abspath(__file__))
+  while os.path.basename(src_dir) != 'src':
+    src_dir = os.path.normpath(os.path.join(src_dir, os.pardir))
+  return src_dir
+
+
+SRC_DIR = FindSrcDirPath()
+sys.path.append(os.path.join(SRC_DIR, 'build'))
+import find_depot_tools
+
+
+def RunGnCommand(args, root_dir=None):
+  """Runs `gn` with provided args and return error if any."""
+  try:
+    command = [
+      sys.executable,
+      os.path.join(find_depot_tools.DEPOT_TOOLS_PATH, 'gn.py')
+    ] + args
+    subprocess.check_output(command, cwd=root_dir)
+  except subprocess.CalledProcessError as err:
+    return err.output
+  return None
+
+
+# GN_ERROR_RE matches the summary of an error output by `gn check`.
+# Matches "ERROR" and following lines until it sees an empty line or a line
+# containing just underscores.
+GN_ERROR_RE = re.compile(r'^ERROR .+(?:\n.*[^_\n].*$)+', re.MULTILINE)
+
+
+def RunGnCheck(root_dir=None):
+  """Runs `gn gen --check` with default args to detect mismatches between
+  #includes and dependencies in the BUILD.gn files, as well as general build
+  errors.
+
+  Returns a list of error summary strings.
+  """
+  out_dir = tempfile.mkdtemp('gn')
+  try:
+    error = RunGnCommand(['gen', '--check', out_dir], root_dir)
+  finally:
+    shutil.rmtree(out_dir, ignore_errors=True)
+  return GN_ERROR_RE.findall(error) if error else []
+
+
+def RunNinjaCommand(args, root_dir=None):
+  """Runs ninja quietly. Any failure (e.g. clang not found) is
+     silently discarded, since this is unlikely an error in submitted CL."""
+  command = [
+              os.path.join(find_depot_tools.DEPOT_TOOLS_PATH, 'ninja')
+            ] + args
+  p = subprocess.Popen(command, cwd=root_dir,
+                       stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+  out, _ = p.communicate()
+  return out
+
+
+def GetClangTidyPath():
+  """POC/WIP! Use the one we have, even it doesn't match clang's version."""
+  tidy = ('third_party/android_ndk/toolchains/'
+          'llvm/prebuilt/linux-x86_64/bin/clang-tidy')
+  return os.path.join(SRC_DIR, tidy)
+
+
+def GetCompilationDb(root_dir=None):
+  """Run ninja compdb tool to get proper flags, defines and include paths."""
+  # The compdb tool expect a rule.
+  commands = json.loads(RunNinjaCommand(['-t', 'compdb', 'cxx'], root_dir))
+  # Turns 'file' field into a key.
+  return {v['file']: v for v in commands}
+
+
+def GetCompilationCommand(filepath, gn_args, work_dir):
+  """Get the whole command used to compile one cc file.
+  Typically, clang++ with flags, defines and include paths.
+
+  Args:
+      filepath: path to .cc file.
+      gen_args: build configuration for gn.
+      work_dir: build dir.
+
+  Returns:
+    Command as a list, ready to be consumed by subprocess.Popen.
+  """
+  gn_errors = RunGnCommand(['gen'] + gn_args + [work_dir])
+  if gn_errors:
+    raise(RuntimeError(
+      'FYI, cannot complete check due to gn error:\n%s\n'
+      'Please open a bug.' % gn_errors))
+
+  # Needed for single file compilation.
+  commands = GetCompilationDb(work_dir)
+
+  # Path as referenced by ninja.
+  rel_path = os.path.relpath(os.path.abspath(filepath), work_dir)
+
+  # Gather defines, include path and flags (such as -std=c++11).
+  try:
+    compilation_entry = commands[rel_path]
+  except KeyError:
+    raise ValueError('%s: Not found in compilation database.\n'
+                     'Please check the path.' % filepath)
+  command = compilation_entry['command'].split()
+
+  # Remove troublesome flags. May trigger an error otherwise.
+  if '-MMD' in command:
+    command.remove('-MMD')
+  if '-MF' in command:
+    index = command.index('-MF')
+    del command[index:index+2]  # Remove filename as well.
+
+  return command
diff --git a/tools_webrtc/presubmit_checks_lib/gn_check_test.py b/tools_webrtc/presubmit_checks_lib/build_helpers_test.py
similarity index 84%
rename from tools_webrtc/presubmit_checks_lib/gn_check_test.py
rename to tools_webrtc/presubmit_checks_lib/build_helpers_test.py
index f7e158cd9b..78973282f9 100755
--- a/tools_webrtc/presubmit_checks_lib/gn_check_test.py
+++ b/tools_webrtc/presubmit_checks_lib/build_helpers_test.py
@@ -11,7 +11,8 @@
 import os
 import unittest
 
-from gn_check import RunGnCheck
+#pylint: disable=relative-import
+import build_helpers
 
 
 TESTDATA_DIR = os.path.join(os.path.dirname(os.path.abspath(__file__)),
@@ -23,7 +24,8 @@ class GnCheckTest(unittest.TestCase):
     test_dir = os.path.join(TESTDATA_DIR, 'circular_dependency')
     expected_errors = ['ERROR Dependency cycle:\n'
                        '  //:bar ->\n  //:foo ->\n  //:bar']
-    self.assertListEqual(expected_errors, RunGnCheck(test_dir))
+    self.assertListEqual(expected_errors,
+                         build_helpers.RunGnCheck(test_dir))
 
 
 if __name__ == '__main__':
diff --git a/tools_webrtc/presubmit_checks_lib/check_orphan_headers_test.py b/tools_webrtc/presubmit_checks_lib/check_orphan_headers_test.py
index 9acf25a517..2dfc18999d 100755
--- a/tools_webrtc/presubmit_checks_lib/check_orphan_headers_test.py
+++ b/tools_webrtc/presubmit_checks_lib/check_orphan_headers_test.py
@@ -11,6 +11,7 @@ import os
 import sys
 import unittest
 
+#pylint: disable=relative-import
 import check_orphan_headers
 
 
diff --git a/tools_webrtc/presubmit_checks_lib/check_package_boundaries_test.py b/tools_webrtc/presubmit_checks_lib/check_package_boundaries_test.py
index 7a5874cf26..abf232e678 100755
--- a/tools_webrtc/presubmit_checks_lib/check_package_boundaries_test.py
+++ b/tools_webrtc/presubmit_checks_lib/check_package_boundaries_test.py
@@ -12,6 +12,7 @@ import ast
 import os
 import unittest
 
+#pylint: disable=relative-import
 from check_package_boundaries import CheckPackageBoundaries
 
 
diff --git a/tools_webrtc/presubmit_checks_lib/gn_check.py b/tools_webrtc/presubmit_checks_lib/gn_check.py
deleted file mode 100644
index 459dcd88ee..0000000000
--- a/tools_webrtc/presubmit_checks_lib/gn_check.py
+++ /dev/null
@@ -1,58 +0,0 @@
-# Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
-#
-# Use of this source code is governed by a BSD-style license
-# that can be found in the LICENSE file in the root of the source
-# tree. An additional intellectual property rights grant can be found
-# in the file PATENTS.  All contributing project authors may
-# be found in the AUTHORS file in the root of the source tree.
-
-import os
-import re
-import shutil
-import subprocess
-import sys
-import tempfile
-
-
-def FindSrcDirPath():
-  """Returns the abs path to the src/ dir of the project."""
-  src_dir = os.path.dirname(os.path.abspath(__file__))
-  while os.path.basename(src_dir) != 'src':
-    src_dir = os.path.normpath(os.path.join(src_dir, os.pardir))
-  return src_dir
-
-
-SRC_DIR = FindSrcDirPath()
-sys.path.append(os.path.join(SRC_DIR, 'build'))
-import find_depot_tools
-
-
-# GN_ERROR_RE matches the summary of an error output by `gn check`.
-# Matches "ERROR" and following lines until it sees an empty line or a line
-# containing just underscores.
-GN_ERROR_RE = re.compile(r'^ERROR .+(?:\n.*[^_\n].*$)+', re.MULTILINE)
-
-
-def RunGnCheck(root_dir=None):
-  """Runs `gn gen --check` with default args to detect mismatches between
-  #includes and dependencies in the BUILD.gn files, as well as general build
-  errors.
-
-  Returns a list of error summary strings.
-  """
-  out_dir = tempfile.mkdtemp('gn')
-  try:
-    command = [
-      sys.executable,
-      os.path.join(find_depot_tools.DEPOT_TOOLS_PATH, 'gn.py'),
-      'gen',
-      '--check',
-      out_dir,
-    ]
-    subprocess.check_output(command, cwd=root_dir)
-  except subprocess.CalledProcessError as err:
-    return GN_ERROR_RE.findall(err.output)
-  else:
-    return []
-  finally:
-    shutil.rmtree(out_dir, ignore_errors=True)