Revert of Update XMLHttpRequest forbidden header names. (https://codereview.chromium.org/378183003/)

Reason for revert:
Caused browser_tests failure
http://build.chromium.org/p/chromium.webkit/builders/Linux%20Tests/builds/37851

    OutOfProcessPPAPITest.URLLoader3
    PPAPINaClGLibcTest.URLLoader3
    PPAPINaClNewlibTest.URLLoader3
    PPAPINaClPNaClTest.URLLoader3
    PPAPITest.URLLoader3


Original issue's description:
> Update XMLHttpRequest forbidden header names.
> 
> See http://fetch.spec.whatwg.org/#forbidden-header-name .
> 
> BUG=373120
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=177762

TBR=abarth@chromium.org,yhirano@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=373120

Review URL: https://codereview.chromium.org/385493002

git-svn-id: svn://svn.chromium.org/blink/trunk@177786 bbb929c8-8fbe-4397-9dbb-9b2b20218538