In https://codereview.chromium.org/1411543011 ("Omnibox: Make Keyword Provide More Generous with Matching"), I added experimental code to make the omnibox more aggressive at providing suggestions from keywords even if the user didn't type the full keyword.  E.g., the input "amazon test" will rank the suggestion for "search amazon.com for test" more strongly than before, strongly enough to likely be displayed.

The experiment evaluating this on desktop was murky.  See bug 566608 for details.  It might be a tiny win but there were effects I don't understand and, given that, it's not worth launching.

However, as Android (and iOS) do not have the tab-to-search feature, allowing keyword suggestions to appear more prominently might be the only way users end up seeing them.  Thus, this experimental code might prove much more valuable on that platform.

I am leaving the experiment code in the code base in hopes that these platforms will make all the UI and other changes to enable keyword suggestions (tracking bug 488898), and then we turn up the ranking knobs easily.

If those platforms end up not enabling the keyword provider, we should remove the code.  (I imagine though that if this is more than a year from the date of filing this bug, we could simply try re-evaluating this change on desktop before doing so.  Maybe the effect will be different?)