Inherit the navigation initiator when navigating instead of the parent/opener

Spec PR: https://github.com/w3c/webappsec-csp/pull/358

Bug: 905301, 894228, 836148
Change-Id: I43ada2266d42d1cd56dbe3c6dd89d115e878a83a
Reviewed-on: https://chromium-review.googlesource.com/c/1314633
Commit-Queue: Andy Paicu <andypaicu@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610850}
void ContentSecurityPolicy::DidReceiveHeader(
    const String& header,
    ContentSecurityPolicyHeaderType type,
    ContentSecurityPolicyHeaderSource source) {
  AddAndReportPolicyFromHeaderValue(header, type, source);

  if (execution_context_)
    ApplyPolicySideEffectsToExecutionContext();
}

void ContentSecurityPolicy::DidReceiveHeader(
    const String& header,
    ContentSecurityPolicyHeaderType type,
    ContentSecurityPolicyHeaderSource source) {
  AddAndReportPolicyFromHeaderValue(header, type, source);

  if (execution_context_)
    ApplyPolicySideEffectsToExecutionContext();
}
