Merge FrameLoader history loading functions

Most of loadSameDocumentItem is unnecessary and loadDifferentDocumentItem is
reasonably short. They're both only called from loadHistoryItem, so merge
them in there.

BUG=none

Review URL: https://chromiumcodereview.appspot.com/23033015

git-svn-id: svn://svn.chromium.org/blink/trunk@156483 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Rename 'prefixed' to 'legacy' in EventTarget::fireEventListeners()

Rename 'prefixed' to 'legacy' in EventTarget::fireEventListeners() now that
legacy but unprefixed events such 'mousewheel' are also handled.

R=arv

Review URL: https://chromiumcodereview.appspot.com/22877036

git-svn-id: svn://svn.chromium.org/blink/trunk@156484 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Update test expectations for dynamic-stylesheet-loading.html

virtual/web-animations-css/animations/dynamic-stylesheet-loading.html times out on Linux

BUG=277005
TEST=none
TBR=steveblock@chromium.org

Review URL: https://codereview.chromium.org/22980025

git-svn-id: svn://svn.chromium.org/blink/trunk@156485 bbb929c8-8fbe-4397-9dbb-9b2b20218538