Port omnibox WebUI to new JS mojom bindings

Usage of the old bindings required loading about 185 kB of JS,
including 155 kB from the common bindings library (mojo_bindings.js)
as well as another ~30 kB from the JS generated by omnibox.mojom.

With the new bindings, the common library is only 21 kB compiled
and the generated JS for omnibox.mojom 16 kB (uncompiled, with lots
of Closure annotations). Net mojom-supporting code size reduction of
80%, with room to improve once we compile generated code too.

Also fixes a long-standing bug in the omnibox JS where the selected
page classification value was not being used.

Bug: 894376
Change-Id: Ie6c5450b7df3b7e7ac29cf68d9a1532c9365046c
Reviewed-on: https://chromium-review.googlesource.com/c/1289701
Commit-Queue: Ken Rockot <[email protected]>
Reviewed-by: Demetrios Papadopoulos <[email protected]>
Cr-Commit-Position: refs/heads/master@{#604509}
7 files changed