BlinkGCPlugin: Fix JSonWriter after Clang r234897

BlinkGCPlugin: Fix JSonWriter after Clang r234897

CompilerInstance::createOutputFile started returning a
raw_pwrite_ostream, which is a super-class of raw_fd_ostream.
We don't really care about the flavour of raw_ostream in JSonWriter,
so just use the base class.

BUG=476343
NOTRY=true

Committed: https://crrev.com/6569bdceb0a1bf6c2510a0b4032095e72581805e
Cr-Commit-Position: refs/heads/master@{#325236}

[hans, 2015-04-15 09:42:22]

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

[hans, 2015-04-15 09:42:23]

Please take a look.

[Nico, 2015-04-15 13:20:04]

On 2015/04/15 09:42:23, hans wrote:
> Please take a look.

Lgtm

[hans, 2015-04-15 13:26:50]

The CQ bit was checked by hans@chromium.org

[commit-bot: I haz the power, 2015-04-15 13:27:09]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1085233002/1

[commit-bot: I haz the power, 2015-04-15 13:30:15]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-15 13:31:11]

Patchset 1 (id:??) landed as
https://crrev.com/6569bdceb0a1bf6c2510a0b4032095e72581805e
Cr-Commit-Position: refs/heads/master@{#325236}