Tighten restrictions on hosted apps calling extension APIs

Only allow component apps to make any API calls, and for them only allow the namespaces they explicitly have permission for (plus chrome.test - I need to see if I can rework some WebStore tests to remove even this). 

BUG=172369


Review URL: https://chromiumcodereview.appspot.com/12095095

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@180426 0039d316-1c4b-4281-b951-d872f2087c98
std::string Extension::GetResourceContentSecurityPolicy(
    const std::string& relative_path) const {
  return IsSandboxedPage(relative_path) ?
      sandboxed_pages_content_security_policy_ : content_security_policy();
}

std::string Extension::GetResourceContentSecurityPolicy(
    const std::string& relative_path) const {
  return IsSandboxedPage(relative_path) ?
      sandboxed_pages_content_security_policy_ : content_security_policy();
}
