CacheStorage: Pass an error object allocated on heap to WebCallbacks::onError (1)

CacheStorage: Pass an error object allocated on heap to WebCallbacks::onError (1)

This is a preliminary patch to simplify memory management in
CallbackPromiseAdapter.

Before this CL, CacheStorageDispatcher passes an error object allocated on stack
to WebCallbacks::onError, and this prevents CallbackPromiseAdapter from uniformly
managing the passed object with a smart pointer.
(All other adapter clients pass an on-heap object)

(1) Chromium: THIS PATCH
(2) Blink: https://codereview.chromium.org/1155573003
(3) Chromium: https://codereview.chromium.org/1150333003
(4) Blink: https://codereview.chromium.org/1150413004

BUG=494884
TEST=n/a

Committed: https://crrev.com/c42996a97da1d32a5a35dd7f09eb82ada88b9b43
Cr-Commit-Position: refs/heads/master@{#334970}

[nhiroki, 2015-06-11 03:21:29]

Patchset #2 (id:20001) has been deleted

[nhiroki, 2015-06-17 08:38:18]

nhiroki@chromium.org changed reviewers:
+ jkarlin@chromium.org

[nhiroki, 2015-06-17 08:38:18]

PTAL, thanks!

[jkarlin, 2015-06-17 11:11:10]

lgtm

[nhiroki, 2015-06-17 23:33:57]

The CQ bit was checked by nhiroki@chromium.org

[commit-bot: I haz the power, 2015-06-17 23:35:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1152003008/1

[commit-bot: I haz the power, 2015-06-18 00:47:29]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-18 00:48:30]

Patchset 1 (id:??) landed as
https://crrev.com/c42996a97da1d32a5a35dd7f09eb82ada88b9b43
Cr-Commit-Position: refs/heads/master@{#334970}