Revert 174424 "Defer style recalc when inserting extension style..."

WebDocumentTest.InsertStyleSheet is crashing at least on Android Debug
bot. See Issue 374901 and Issue 374162.

> Defer style recalc when inserting extension stylesheets.
> 
> StyleEngine::addAuthorSheet, used when injecting stylesheets from extensions,
> was doing a synchronous style recalc. Adding two stylesheets in a row would
> cause two style recalcs. Do a deferred style recalc instead.
> 
> BUG=374901,374162
> 
> Review URL: https://codereview.chromium.org/290563007

TBR=rune@opera.com

Review URL: https://codereview.chromium.org/294473007

git-svn-id: svn://svn.chromium.org/blink/trunk@174434 bbb929c8-8fbe-4397-9dbb-9b2b20218538