In NonAllocatingMap, remove asserts around key/value length.

Since the data is stored using strncpy they are merely advisory in debug mode.

BUG=https://code.google.com/p/chromium/issues/detail?id=298225
R=mark@chromium.org

Review URL: https://breakpad.appspot.com/635002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1219 4c0a9323-5329-0410-9bdc-e9ce6186880e