Remove some DCHECK/NOTREACHED from plugin_host.cc that can be hit by valid code
Remove some DCHECK/NOTREACHED from plugin_host.cc that can be hit by valid code

I hit these checks while trying to debug a webpage that happened to include some flash content.  These checks don't seem to indicate any bug in chrome and we handle the codepath fine in release, so they just seem like a debugging hindrance.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/4514001

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@65171 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser