Revert 264167 "Sniff MIME type for files which have unknown exte..."

Revert 264167 "Sniff MIME type for files which have unknown exte..."

This revert is requested by fukino, who is the author of the patch.

This patch breaks a browser test on Windows. 

> Sniff MIME type for files which have unknown extensions.
> 
> What I want to do:
> Open text files which have unknown extensions(e.g. access.log.1) using packaged apps which can handle 'text/plain'(e.g. Text, Caret,...).
> 
> Current situation:
> By following reasons, text files with unknow extension can't be opened.
> 1. FileManager guess the MIME type as empty, so 'text/plain'-supporting apps are not shown as handlers.
> 2. PlatformAppLauncher guess the MIME type as 'application/octet-stream', and it launch apps with no data because those apps don't handle 'application/octet-stream'.
> 
> What I changed:
> Modified FileManager and PlatformAppLauncher to sniff MIME types if they are unknown based on extensions.
> 
> BUG=352250
> R=benwells@chromium.org, hashimoto@chromium.org, jorgelo@chromium.org
> 
> Review URL: https://codereview.chromium.org/224883008
> 
> Patch from Naoki Fukino <fukino@chromium.org>;.

TBR=yoshiki@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=264192

[yoshiki, 2014-04-16 14:04:19]

Committed patchset #1 manually as r264192 (tree was closed).