Add web dev style guide presubmit checks and --fix support.

PRESUBMIT.py

@@ -6,6 +6,8 @@
 import os
 import sys
 
+import override_utils
+
 USE_PYTHON3 = True
 PRESUBMIT_VERSION = '2.0.0'
 
@@ -124,3 +126,20 @@ def CheckLicense(input_api, output_api):
             output_api.PresubmitPromptWarning(expected_license_message,
                                               items=bad_files))
     return result
+
+
+def CheckWebDevStyle(input_api, output_api):
+    results = []
+    try:
+        old_sys_path = sys.path[:]
+        cwd = input_api.PresubmitLocalPath()
+        sys.path += [input_api.os_path.join(cwd, '..', 'tools')]
+        # pylint: disable=import-error, import-outside-toplevel
+        from web_dev_style import presubmit_support
+        with override_utils.override_scope_variable(output_api,
+                                                    'PresubmitPromptWarning',
+                                                    output_api.PresubmitError):
+            results += presubmit_support.CheckStyle(input_api, output_api)
+    finally:
+        sys.path = old_sys_path
+    return results