clang/win: For 64-bit builds, enable warnings-as-errors and stop falling back to CL.

clang/win: For 64-bit builds, enable warnings-as-errors and stop falling back to CL.

Clang can now build all of chrome's translation units in 64-bit.  Remove
/fallback so that the bot will turn red if this regresses.

Also turn on warnings-as-errors, so that warnings also turn the build red
(instead of just causing a fallback as before).

Also remove a superfluous 'RuntimeTypeInfo': 'false': This is already the
default for non-clang builds too.  (And for the few places where we do need
RTTI -- icu -- clang has been able to emit it for months now.)

BUG=82385
R=hans@chromium.org

Committed: https://chromium.googlesource.com/chromium/src/+/5e66594551c7bbeda37cb640314d24429387ae3b

[Nico, 2015-02-13 01:50:28]

thakis@chromium.org changed reviewers:
+ hans@chromium.org

[Nico, 2015-02-13 01:50:29]

!!!

[hans, 2015-02-13 02:00:59]

lgtm!!!

[commit-bot: I haz the power, 2015-02-13 03:00:51]

Patchset 3 (id:??) landed as
https://crrev.com/5e66594551c7bbeda37cb640314d24429387ae3b
Cr-Commit-Position: refs/heads/master@{#316141}

[Nico, 2015-02-13 03:00:58]

Committed patchset #3 (id:40001) manually as
5e66594551c7bbeda37cb640314d24429387ae3b (presubmit successful).