InstantService: on creation, immediately query TopSites
InstantService: on creation, immediately query TopSites

Before, we'd only get the TopSites on the first "Change" event. If TopSites happens to be initialized before InstantService, then that might take a while (see bug).

BUG=476734

Review URL: https://codereview.chromium.org/1552563002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#372659}

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