[fsp] Do not close files which failed to open for reading and writing.

[fsp] Do not close files which failed to open for reading and writing.

This CL fixes the logic for detecting if a file was correctly opened in the
fsp::FileStreamReader and fsp::FileStreamWriter classes.

TEST=browser_test: *FileSystemProvider*, unit_test: *FileSystemProvider*FileStream*
BUG=447448
Committed: https://crrev.com/8b8e1fac50acf7f2245b96b1f30353fb41ac8de8
Cr-Commit-Position: refs/heads/master@{#310713}

[mtomasz, 2015-01-09 04:21:28]

mtomasz@chromium.org changed reviewers:
+ yawano@chromium.org

[mtomasz, 2015-01-09 04:21:36]

@yawano: PTAL. Thanks!

[yawano, 2015-01-09 04:49:00]

lgtm. Thank you!

[mtomasz, 2015-01-09 04:57:20]

The CQ bit was checked by mtomasz@chromium.org

[commit-bot: I haz the power, 2015-01-09 04:58:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/814113007/1

[commit-bot: I haz the power, 2015-01-09 05:05:38]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-09 05:06:28]

Patchset 1 (id:??) landed as
https://crrev.com/8b8e1fac50acf7f2245b96b1f30353fb41ac8de8
Cr-Commit-Position: refs/heads/master@{#310713}