Revert 184411 "The link shoud be activated by enter key on focus..."

This caused chromium.webkit non-layout OSX 10.6/10.8 bots,
failing WebViewInteractiveTest.NewWindow_OpenInNewTab of
interactive_ui_tests.

Miyoung, my suggestion is to use trybots for non-blink builders
(e.g. linux_chromium_dbg, mac_chromium_dbg etc.) to make sure this does not
break Chromium builders.  Blink commit queue only runs through
Blink builders and they don't run interactive_ui_tests.

> The link shoud be activated by enter key on focusing the child element inside the anchor.
> This makes behaviour consistent with firefox and IE.
> 
> BUG=350738
> R=pdr@chromium.org
> R=rob@robwu.nl
> TEST=LayoutTests/fast/events/keydown-enter-key-on-focused-element-inside-link.html
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=184074
> 
> Review URL: https://codereview.chromium.org/619613005

TBR=myid.o.shin@gmail.com
BUG=425859

Review URL: https://codereview.chromium.org/676893004

git-svn-id: svn://svn.chromium.org/blink/trunk@184423 bbb929c8-8fbe-4397-9dbb-9b2b20218538