Revert of Removed virtualenv from depot_tools

third_party/protobuf26/README.chromium

 This directory contains google.protobuf module version 2.6.0 build 0.
 
 sergiyb@: It has been manually renamed to protobuf26. This is needed to avoid
 conflicts with a built-in google.protobuf module found on many developer
-machines. The long-term solution to this problem was to use virtualenv and it
-was implemented, but had to be reverted due to incompatibilities with ChromiumOS
-builds (see http://crbug.com/542922).
+machines. The long-term solution to this problem, however, should be virtualenv.
+Unfortunately due to limited time and lack of experience, it was not a
+reasonable short-term solution.
 
-If you need to update this package, please make sure that you replace all the
-references to google.protobuf in the package itself with protobuf26, e.g.
+If you need to update this package, please make sure that you replace all
+the references to google.protobuf in the package itself with protobuf26, e.g.
 
   from google.protobuf import text_format
   import google.protobuf
 
 becomes
 
   from protobuf26 import text_format
   import protobuf26
 
-Original bug tracking setting up virtualenv for depot_tools was
-http://crbug.com/503067, but it was closed as WontFix. If you believe that
-virtualenv should be added to the current version of depot_tools, please re-open
-that bug.
+Bug tracking setting up virtualenv for depot_tools is https://crbug.com/496241.