Revert of DevTools: Support async call stacks for FileSystem API (part 1).

Revert of DevTools: Support async call stacks for FileSystem API (part 1). (https://codereview.chromium.org/383123009/)

Reason for revert:
This seems to add a lot of complexity into async code + violates the modularity: core/inspector should not be aware of the filesystems.

Original issue's description:
> DevTools: Support async call stacks for FileSystem API (part 1).
> 
> This patch does not yet tracks async stacks for FileWriter and FileReader.
> 
> BUG=272416, 390863
> R=kinuko@chromium.org, nhiroki@chromium.org, yurys
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=178149

TBR=kinuko@chromium.org,nhiroki@chromium.org,yurys@chromium.org,aandrey@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=272416, 390863
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=178269

[pfeldman, 2014-07-16 12:09:59]

Created Revert of DevTools: Support async call stacks for FileSystem API (part
1).

[commit-bot: I haz the power, 2014-07-16 12:10:58]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/pfeldman@chromium.org/397843009/1

[commit-bot: I haz the power, 2014-07-16 12:11:35]

Change committed as 178269