Revert of Add option to disable navigation on drag drop (https://codereview.chromium.org/147493016/)

Reason for revert:
WebViewTest.DragDropURL crashes on WebKit Android (Nexus4):

http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Android%20%28Nexus4%29/builds/9268/steps/webkit_unit_tests/logs/stdio

Original issue's description:
> Add option to disable navigation on drag drop
> 
> BUG=342394
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166940

TBR=fsamuel@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=342394

Review URL: https://codereview.chromium.org/150203010

git-svn-id: svn://svn.chromium.org/blink/trunk@166943 bbb929c8-8fbe-4397-9dbb-9b2b20218538