Clean up in browser side of allowFileSystem. [chromium] (4/4)

Clean up in browser side of allowFileSystem.
Remove unused part for shared worker.


Solve conflicts from rebase.

Conflicts:
	chrome/renderer/content_settings_observer.cc
	chrome/renderer/content_settings_observer.h

BUG=343382
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=272850

[Xi Han, 2014-05-16 21:57:36]

Currently there are 4 CLs for filesystem permission implementation for WebView,
and this is the last one. To avoid the confusion, I list the order of these CLs
and hopefully it will make reviewing them easier :

1. rename in blink: 
    Issue 289793002:Rename sync and async file system access methods in blink
    https://codereview.chromium.org/289793002/

2. implementation in browser side:
    Issue 273513005: Avoid sync IPCs for FileSystem API
    https://codereview.chromium.org/273513005/

3. clean up in blink:
    Issue 277353002: Use asynchronized api for file system request.
    https://codereview.chromium.org/277353002/

4. clean up in browser:
    Issue 290573010: Clean up in browser side of allowFileSystem.
    https://codereview.chromium.org/290573010/

[kinuko, 2014-05-19 09:03:31]

lgtm

[jochen (gone - plz use gerrit), 2014-05-19 13:23:16]

lgtm

[Xi Han, 2014-05-26 01:44:54]

The CQ bit was checked by hanxi@chromium.org

[commit-bot: I haz the power, 2014-05-26 01:45:48]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/hanxi@chromium.org/290573010/40001

[commit-bot: I haz the power, 2014-05-26 16:34:11]

Change committed as 272850