Check that a plugin path points to a file before rejecting the plugin because it's 64-bit.
Check that a plugin path points to a file before rejecting the plugin because it's 64-bit.

BUG=75131
TEST=none

Review URL: http://codereview.chromium.org/6635013
Patch from Simon Morris <simonmorris@chromium.org>.

git-svn-id: http://src.chromium.org/svn/trunk/src@77186 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 128adb8b5c5b3714296c996b66501d218a047fcd
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser