PY3 migration(blink web tests) - Fix PY3 issues on windows

Added pywin32 wheel.
Fix _winreg.

Currently pywebsocket is not bringing up the server. Will take it up after this.
Bug: 1197679

Change-Id: I667a7e84c39f90f4aa0fc4b542e0a5e4d648f6f6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3084017
Commit-Queue: Preethi Mohan <preethim@google.com>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Cr-Commit-Position: refs/heads/master@{#911789}

.vpython3

@@ -251,3 +251,16 @@ wheel: <
     platform: "linux_armv7l"
   >
 >
+
+# Used by:
+#   //third_party/blink/tools/blinkpy/web_tests/port/server_process.py
+wheel: <
+  name: "infra/python/wheels/pywin32/${vpython_platform}"
+  version: "version:300"
+  match_tag: <
+    platform: "win32"
+  >
+  match_tag: <
+    platform: "win_amd64"
+  >
+>

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

@@ -35,7 +35,7 @@ import tempfile
 # The _winreg library is only available on Windows.
 # https://docs.python.org/2/library/_winreg.html
 try:
-    import _winreg  # pylint: disable=import-error
+    import six.moves.winreg as _winreg  # pylint: disable=import-error
 except ImportError:
     _winreg = None  # pylint: disable=invalid-name
 
@@ -185,7 +185,9 @@ class WinPort(base.Port):
         # program name to find the working one.
         _log.debug('Searching for Python 3 command name')
 
-        exts = filter(len, os.getenv('PATHEXT', '').split(';'))
+        exts = [
+            path for path in os.getenv('PATHEXT', '').split(';') if len(path)
+        ]
         for ext in [''] + exts:
             python = 'python3%s' % ext
             _log.debug('Trying "%s"' % python)