Revert 239759 "The comment in base64.h implies that base::Base64..."

Revert 239759 "The comment in base64.h implies that base::Base64..."

> The comment in base64.h implies that base::Base64Encode() can return false, but
> this cannot happen in practice. Fix the comment.
> 
> The implementation of Base64Encode() attempts to check for the return value
> MODP_B64_ERROR as a failure, but modp_b64_encode() cannot return this
> value. Remove the check.
> 
> Remove unneeded integer cast.
> 
> Change the return type to void.
> 
> BUG=323357
> TEST=base_unittests, compile all
> TBR=jochen@chromium.org,miket@chromium.org,joi@chromium.org,akalin@chromium.org,sergeyu@chromium.org
> 
> Review URL: https://codereview.chromium.org/86913002

TBR=ricea@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=239921

[vadimt, 2013-12-11 00:03:37]

Committed patchset #1 manually as r239921.

[vadimt, 2013-12-11 00:14:14]

The reason for reverting was a hard-to-diagnose failure on Chromium ChromiumOS
on Linux ChromiumOS Tests (dbg)(2).
We, sheriffs, decided to rollback some of CLs to see whether this fixes the
build.
Sorry if your CL wasn't the cause of the failure :(