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This CL nukes ContentBrowserClient::CreateGeolocationDelegate()
and their overrides, and transfers each embedder's callsite to the
appropriate correspondent BrowserMainParts. These embedders are
namely: android_webview,  blimp, cast, chrome and content_shell.

Continuation of https://crrev.com/2127973002/.

BUG=612334

Review-Url: https://codereview.chromium.org/2174613002
Cr-Commit-Position: refs/heads/master@{#407291}