This patch implements a mechanism for more granular link URL permissions (filtering on scheme/host). This fixes the bug that allowed PDFs to have working links to any "chrome://" URLs.

BUG=528505,226927

Review URL: https://codereview.chromium.org/1362433002

Cr-Commit-Position: refs/heads/master@{#351705}
  ~SecurityState() {
    scheme_policy_.clear();
    storage::IsolatedContext* isolated_context =
        storage::IsolatedContext::GetInstance();
    for (FileSystemMap::iterator iter = filesystem_permissions_.begin();
         iter != filesystem_permissions_.end();
         ++iter) {
      isolated_context->RemoveReference(iter->first);
    }
    UMA_HISTOGRAM_COUNTS("ChildProcessSecurityPolicy.PerChildFilePermissions",
                          file_permissions_.size());
   }

  ~SecurityState() {
    scheme_policy_.clear();
    storage::IsolatedContext* isolated_context =
        storage::IsolatedContext::GetInstance();
    for (FileSystemMap::iterator iter = filesystem_permissions_.begin();
         iter != filesystem_permissions_.end();
         ++iter) {
      isolated_context->RemoveReference(iter->first);
    }
    UMA_HISTOGRAM_COUNTS("ChildProcessSecurityPolicy.PerChildFilePermissions",
                          file_permissions_.size());
   }
