Servo's \`WebView::set_history\` fires \`notify_url_changed\` on **every**
history mutation — full navigations, redirects, in-page link clicks,
and JS-driven \`history.pushState\` / \`history.replaceState\`.
Our pipeline fans that delegate signal back through
\`WebSurfaceUrlChange\` into \`tab.url\`. The next \`ensure_surface\`
observes the new tab URL, hashes a fresh ensure key, and calls
\`ServoLiveClient::ensure\` → \`apply_navigation\`. Until this commit
\`apply_navigation\` compared the request against the local
\`session.requested_url\` cache and, on mismatch, sent Servo a
\`webview.load(url)\` — even when Servo was the one who *just*
told us about that URL.
\`WebView::load\` is a hard navigation: it tells the constellation
to abort the current document, clear the surface, and refetch.
google.com's homepage \`replaceState\`s a fresh \`?zx=<timestamp>\`
roughly once a second to bust caches; with this round-trip we
were turning each of those into a full load-clear-refetch and
producing one visible white flash per second.
Use \`host.snapshot(webview_id).url()\` (which Servo keeps in lock-step
with \`set_history\`) as the source of truth. If Servo's WebView is
already at the requested URL, just sync our \`session.requested_url\`
bookkeeping and return — no \`load\` message, no surface clear, no
flash. Genuine embedder-initiated navigations (chrome URL bar typed,
in-app link click) still take the \`should_navigate\` path because
Servo's URL hasn't caught up to the requested target yet.
ZacharyZhang-NY
7fc2967793