remove use of {,un}setPendingActivity from DOMFileSystem.

remove use of {,un}setPendingActivity from DOMFileSystem.

{,un}setPendingActivity is deprecated. This CL replaces it with |hasPendingActivity()| override.

This also makes FileSystemCallbacks reference to the DOMFileSystem strong, as |addPendingCallbacks()| would no longer ref() DOMFileSystem.

TEST=fast/filesystem
BUG=354845
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170052

[haraken, 2014-03-26 06:49:09]

LGTM

[wibling-chromium, 2014-03-26 08:45:18]

lgtm

[zerny-chromium, 2014-03-26 09:16:33]

lgtm

[kouhei (in TOK), 2014-03-26 09:17:41]

kinuko: Would you also take a look?

[kinuko, 2014-03-26 11:59:15]

On 2014/03/26 09:17:41, kouhei wrote:
> kinuko: Would you also take a look?

lgtm, sorry for slow response

[kouhei (in TOK), 2014-03-26 12:14:49]

The CQ bit was checked by kouhei@chromium.org

[commit-bot: I haz the power, 2014-03-26 12:14:56]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/kouhei@chromium.org/212263002/1

[commit-bot: I haz the power, 2014-03-26 12:25:12]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-03-26 12:25:12]

Try jobs failed on following builders:
  tryserver.blink on win_blink_compile_dbg

[kouhei (in TOK), 2014-03-26 12:33:31]

The CQ bit was checked by kouhei@chromium.org

[commit-bot: I haz the power, 2014-03-26 12:33:39]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/kouhei@chromium.org/212263002/1

[commit-bot: I haz the power, 2014-03-26 12:58:28]

Change committed as 170052