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}
void ChildProcessSecurityPolicyImpl::RegisterPseudoScheme(
    const std::string& scheme) {
  base::AutoLock lock(lock_);
  DCHECK_EQ(0U, pseudo_schemes_.count(scheme)) << "Add schemes at most once.";
  DCHECK_EQ(0U, web_safe_schemes_.count(scheme))
      << "Pseudo implies not web-safe.";

  pseudo_schemes_.insert(scheme);
}

void ChildProcessSecurityPolicyImpl::RegisterPseudoScheme(
    const std::string& scheme) {
  base::AutoLock lock(lock_);
  DCHECK_EQ(0U, pseudo_schemes_.count(scheme)) << "Add schemes at most once.";
  DCHECK_EQ(0U, web_safe_schemes_.count(scheme))
      << "Pseudo implies not web-safe.";

  pseudo_schemes_.insert(scheme);
}
