Rewrite SimpleStringDictionary with NonAllocatingMap.

NonAllocatingMap has a near-identical interface, but is significantly less code,
more customizable, and has storage that is POD.

BUG=http://code.google.com/p/chromium/issues/detail?id=77656

Review URL: https://breakpad.appspot.com/568002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1161 4c0a9323-5329-0410-9bdc-e9ce6186880e