Make code slightly less complicated.

idl_files_list contains the contents of idl_files, so `cat <(idl_files_list)`
will always evaluate to idl_files. No need to shell out to cat for this.

No functionality change. This was added in
https://bugs.webkit.org/show_bug.cgi?id=73394

BUG=none
R=haraken@chromium.org

Review URL: https://codereview.chromium.org/26980003

git-svn-id: svn://svn.chromium.org/blink/trunk@159558 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Revert 159545 "Adding derived sources for platform."

> Adding derived sources for platform.
> 
> Pending moves from core/platform to platform have a dependency on
> derived sources. Add support in this changelist.
> 
> R=abarth@chromium.org, abarth, eseidel
> BUG=297477
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=159354
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=159389
> 
> Review URL: https://codereview.chromium.org/26697002

Crashing multiple layout tests.

http/tests/appcache/404-manifest.html
http/tests/appcache/404-resource.html
http/tests/appcache/abort-cache-onchecking-manifest-404.html
http/tests/appcache/abort-cache-onchecking-resource-404.html
...

TBR=schenney@chromium.org

Review URL: https://codereview.chromium.org/26681003

git-svn-id: svn://svn.chromium.org/blink/trunk@159559 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Layout Test fast/js/JSON-stringify.html is failing

Test started failing on Mac Release consitently after Blink
r159506 landed.

TBR=tkent
NOTRY=true
BUG=306929

Review URL: https://codereview.chromium.org/27150002

git-svn-id: svn://svn.chromium.org/blink/trunk@159560 bbb929c8-8fbe-4397-9dbb-9b2b20218538