Fail the web app manifest fetch if the document is sandboxed.

This ensures that sandboxed pages are regarded as non-PWAs, and that
other features in the browser process which trust the web manifest do
not receive the manifest at all if the document itself cannot access the
manifest.

BUG=771709

Change-Id: Ifd4d00c2fccff8cc0e5e8d2457bd55b992b0a8f4
Reviewed-on: https://chromium-review.googlesource.com/866529
Commit-Queue: Dominick Ng <dominickn@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Cr-Commit-Position: refs/heads/master@{#531121}
void ManifestManager::DidCommitProvisionalLoad(
    bool is_new_navigation,
    bool is_same_document_navigation) {
  if (is_same_document_navigation)
    return;

  may_have_manifest_ = false;
  manifest_dirty_ = true;
  manifest_url_ = GURL();
 }

void ManifestManager::DidCommitProvisionalLoad(
    bool is_new_navigation,
    bool is_same_document_navigation) {
  if (is_same_document_navigation)
    return;

  may_have_manifest_ = false;
  manifest_dirty_ = true;
  manifest_url_ = GURL();
 }
