Inherit CSP when we inherit the security origin

This prevents attacks that use main window navigation to get out of the
existing csp constraints such as the related bug

Bug: 747847
Change-Id: I1e57b50da17f65d38088205b0a3c7c49ef2ae4d8
Reviewed-on: https://chromium-review.googlesource.com/592027
Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Andy Paicu <andypaicu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#492333}
bool Document::IsSecureContext() const {
  bool is_secure = IsSecureContextImpl();
  if (GetSandboxFlags() != kSandboxNone) {
    UseCounter::Count(
        *this, is_secure
                   ? WebFeature::kSecureContextCheckForSandboxedOriginPassed
                   : WebFeature::kSecureContextCheckForSandboxedOriginFailed);
  }
  UseCounter::Count(*this, is_secure ? WebFeature::kSecureContextCheckPassed
                                     : WebFeature::kSecureContextCheckFailed);
  return is_secure;
}

bool Document::IsSecureContext() const {
  bool is_secure = IsSecureContextImpl();
  if (GetSandboxFlags() != kSandboxNone) {
    UseCounter::Count(
        *this, is_secure
                   ? WebFeature::kSecureContextCheckForSandboxedOriginPassed
                   : WebFeature::kSecureContextCheckForSandboxedOriginFailed);
  }
  UseCounter::Count(*this, is_secure ? WebFeature::kSecureContextCheckPassed
                                     : WebFeature::kSecureContextCheckFailed);
  return is_secure;
}
