Reorganize apps/shell into app, browser and common directories

Reorganize apps/shell into app, browser and common directories.

This allows us to separate browser process, render process and common code, similar to how content/shell is organized.  This also allows the DEPS files to be more restrictive to enforce those dependencies.

A parallel CL adds apps/shell/renderer and some renderer-specific code: https://codereview.chromium.org/149163002/

BUG=none
TEST=compiles
R=joi@chromium.org, miket@chromium.org
TBR=stevenjb@chromium.org for DEPS on src/chromeos (just moving the DEP from one file to another)

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=248575

[James Cook, 2014-02-01 00:49:20]

joi, PTAL at the DEPS file structure. I split apps/shell/DEPS into apps, browser
and common versions.

Everything else is just moving files into subdirectories.

https://codereview.chromium.org/151893002/diff/40001/apps/shell/app/README
File apps/shell/app/README (right):

https://codereview.chromium.org/151893002/diff/40001/apps/shell/app/README#ne...
apps/shell/app/README:3: This directory has nothing to do with the
apps/extensions themselves.
I thought the path "apps/shell/app" was confusing, since the first "app" and the
second "app" mean different things, so I added this README.

[Jói, 2014-02-03 10:43:13]

LGTM

https://codereview.chromium.org/151893002/diff/100001/apps/DEPS
File apps/DEPS (right):

https://codereview.chromium.org/151893002/diff/100001/apps/DEPS#newcode3
apps/DEPS:3: "+content/public/browser",
Would it make sense to use more restrictive DEPS for //content/public/browser at
the top level? OK like this if you prefer, as long as //content/public/renderer
has a -content/public/browser.

[James Cook, 2014-02-03 17:41:56]

miket, can I get OWNERS for apps/apps.gypi?

(I've also sent you a CL to extend owners for that particular file so I don't
have to bug you guys for these sorts of renames/file adds.)

[miket_OOO, 2014-02-03 18:39:06]

On 2014/02/03 17:41:56, James Cook wrote:
> miket, can I get OWNERS for apps/apps.gypi?
> 
> (I've also sent you a CL to extend owners for that particular file so I don't
> have to bug you guys for these sorts of renames/file adds.)

OWNER LGTM

[James Cook, 2014-02-03 21:19:57]

Committed patchset #4 manually as r248575 (presubmit successful).