Make Isolated file system writable only if it is configured so

Make Isolated file system writable only if it is configured so

- Use CreateFileStreamWriter in FSO
- Add yet another write-protection at IsolatedContext (in addition to ChildProcessSecurityPolicy, so that we can make each fs read-only or writable in DRT/testing)

BUG=none
TEST=none (will add layout_test)

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=141395

[kinuko, 2012-06-08 04:05:34]

Preparing for making isolated fs writable.

[kinuko, 2012-06-08 04:05:45]

On 2012/06/08 04:05:34, kinuko wrote:
> Preparing for making isolated fs writable.

Can you take a look?

[kinaba, 2012-06-08 04:40:19]

http://codereview.chromium.org/10540070/diff/1/webkit/fileapi/isolated_contex...
File webkit/fileapi/isolated_context.cc (right):

http://codereview.chromium.org/10540070/diff/1/webkit/fileapi/isolated_contex...
webkit/fileapi/isolated_context.cc:122: return false;
I failed to understand these two lines.
It looks like "if it is not writable right now, return false". Maybe something
other than writable_ids_ should be looked up?

[kinuko, 2012-06-08 05:24:24]

http://codereview.chromium.org/10540070/diff/1/webkit/fileapi/isolated_contex...
File webkit/fileapi/isolated_context.cc (right):

http://codereview.chromium.org/10540070/diff/1/webkit/fileapi/isolated_contex...
webkit/fileapi/isolated_context.cc:122: return false;
On 2012/06/08 04:40:19, kinaba wrote:
> I failed to understand these two lines.
> It looks like "if it is not writable right now, return false". Maybe something
> other than writable_ids_ should be looked up?

Aha you're right.  I was first writing this patch like permission_mask_map_ and
then revised it , but failed to update this line... (hmm maybe I need a test)

Fixed.

[kinuko, 2012-06-08 07:44:26]

On 2012/06/08 05:24:24, kinuko wrote:
>
http://codereview.chromium.org/10540070/diff/1/webkit/fileapi/isolated_contex...
> File webkit/fileapi/isolated_context.cc (right):
> 
>
http://codereview.chromium.org/10540070/diff/1/webkit/fileapi/isolated_contex...
> webkit/fileapi/isolated_context.cc:122: return false;
> On 2012/06/08 04:40:19, kinaba wrote:
> > I failed to understand these two lines.
> > It looks like "if it is not writable right now, return false". Maybe
something
> > other than writable_ids_ should be looked up?
> 
> Aha you're right.  I was first writing this patch like permission_mask_map_
and
> then revised it , but failed to update this line... (hmm maybe I need a test)
> 
> Fixed.

Added simple tests.

[kinaba, 2012-06-08 07:56:40]

lgtm