Synthesize an extra AutocompleteSuggestion at the top of the Search
Suggestions section whenever there is a configured search engine and
the typed query is not URL-shaped.
Use the query as the row's primary text, carry a "Search with <engine>"
subtitle, and render that subtitle in the AppKit and Qt popups so the
explicit search fallback stays visible and readable even when history
fills the list.
Replace the frontend-facing Vector<String> flow with structured
AutocompleteSuggestion objects carrying source, section, title,
and favicon metadata.
Build merged history and literal-URL rows in LibWebView, deduplicate
equivalent URL suggestions, move the autocomplete URL helpers out
of URL.h, and update the history and URL tests around the new model.
Teach LibWebView autocomplete to query HistoryStore before falling back
to remote engines and move the wiring out of the AppKit frontend.
Refine matching so scheme and www. boilerplate do not dominate results,
short title and substring queries stay quiet, and history tracing can
explain what the ranking code is doing.
For example, Google uses ISO-8859-1 encoding. This patch allows us to
decode such responses, falling back to UTF-8 if a Content-Type was not
specified or could not be parsed. We should also now handle if decoding
fails, rather than crashing inside JsonParser.
This implements an autocomplete engine inside LibWebView, to replace the
engine currently used by Qt. Whereas Qt uses the Qt Network framework to
perform autocomplete requests, LibWebView uses RequestServer. This moves
downloading this untrusted data out of the browser process.
This patch only implements the persisted settings and their UI. It does
not integrate this engine into the browser UI.
