Update content/ to use WeakPtr<T>::get() instead of implicit "operator T*"

BUG=245942
[email protected]

Review URL: https://codereview.chromium.org/16256018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@203775 0039d316-1c4b-4281-b951-d872f2087c98
27 files changed