Make uninstall_chrome.py look in the right registry hive.

When run using a 64-bit build of python.exe, the tool needs to
explicitly look in the 32-bit hive for Chrome's uninstall key.

BUG=822448

Change-Id: Icc0274f73411a717878651ec50ad65e7292f3102
Reviewed-on: https://chromium-review.googlesource.com/966444
Commit-Queue: Stephen Martinis <martiniss@chromium.org>
Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543800}

chrome/test/mini_installer/uninstall_chrome.py

@@ -38,7 +38,8 @@ def main():
              options.chrome_long_name)
   # Query the key. It will throw a WindowsError if the key doesn't exist.
   try:
-    key = _winreg.OpenKey(root_key, sub_key, 0, _winreg.KEY_QUERY_VALUE)
+    key = _winreg.OpenKey(root_key, sub_key, 0,
+                          _winreg.KEY_QUERY_VALUE | _winreg.KEY_WOW64_32KEY)
   except WindowsError:
     if options.no_error_if_absent:
       return 0