Revert "Change event handling order in HTMLPlugInElement."

This reverts commit fada04e1ba92f2e951341da3ef52145dc96297bf.

This change affected the behavior of flash on google maps. I'm reverting this
for now to get rid of this regression. I hope to address this in a future change
by altering this behavior only for non-Flash PPAPI applications.

BUG=324351,356089
TBR=eseidel

Review URL: https://codereview.chromium.org/212893005

git-svn-id: svn://svn.chromium.org/blink/trunk@170336 bbb929c8-8fbe-4397-9dbb-9b2b20218538