Revert of GN: Explicitly list out public headers in the blink_headers source_set

Revert of GN: Explicitly list out public headers in the blink_headers source_set (patchset #2 id:20001 of https://codereview.chromium.org/1222673004/)

Reason for revert:
This patch is causing build failures:
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_gn_rel/builds/107230/steps/gn_check%20%28with%20patch%29/logs/stdio

Original issue's description:
> GN: Explicitly list out public headers in the blink_headers source_set
> 
> This enables "gn check" to enforce that source files that #include
> these headers also declare a dependency on them in GN.
> 
> This also fixes "gn check" on Android from having errors like:
> 
> ERROR at //components/autofill/content/renderer/autofill_agent.cc:45:11: Include not allowed.
>           ^--------------------------------------------
> It is not in any dependency of
>   //components/autofill/content/renderer:renderer
> The include file is in the target(s):
>   //third_party/WebKit/public:blink_headers_java_enums_srcjar__generate_enum
> which should somehow be reachable.
> 
> BUG=367595
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=198439

TBR=dpranke@chromium.org,esprehn@chromium.org,agrieve@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=367595
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=198520

[pdr., 2015-07-08 17:59:46]

Created Revert of GN: Explicitly list out public headers in the blink_headers
source_set

[commit-bot: I haz the power, 2015-07-08 18:00:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1224843009/1

[commit-bot: I haz the power, 2015-07-08 18:00:46]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=198520

[agrieve, 2015-07-08 22:32:45]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1228703004/ by agrieve@chromium.org.

The reason for reverting is: Re-landing now that
https://crrev.com/deb02768bf9805279461259119a845aa2c734e25 is landed (fixes the
gn check errors this introduced the first time around).