Revert of Remove support for legacy WebKit Notifications (https://codereview.chromium.org/184733002/)

Reason for revert:
Broke interactive_ui_tests and browser_tests, as pointed out by cbiesinger.

http://build.chromium.org/p/chromium.webkit/builders/Linux%20Tests/builds/35005

Original issue's description:
> Remove support for legacy WebKit Notifications
> 
> This patch removes support for the legacy WebKit notifications from Blink,
> per the following Intent to Remove thread:
> 
> https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/8vqyfHa8_dw
> 
> BUG=348019
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=168471

TBR=atwilson@chromium.org,jochen@chromium.org,abarth@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=348019

Review URL: https://codereview.chromium.org/187323005

git-svn-id: svn://svn.chromium.org/blink/trunk@168486 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Oilpan: fix build after changes that did not take oilpan into account.

R=haraken@chromium.org, wibling@chromium.org
TBR=betravis@adobe.com, haraken@chromium.org, wibling@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/184293008

git-svn-id: svn://svn.chromium.org/blink/trunk@168487 bbb929c8-8fbe-4397-9dbb-9b2b20218538