Wait for the load event in TestRestoreAfterGeometrycacheChange.

BUG=324915

Review URL: https://codereview.chromium.org/100393008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238675 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238675