Change CreateBrowserMainParts to return unique_ptrs

The caller is already assumed to take on ownership of the
return value (See browser_main_loop.cc). Wrapping it in a
unique_ptr makes this explicit.

Tbr: tapted@chromium.org
Tbr: thakis@chromium.org
Tbr: seantopping@chromium.org
Tbr: rdevlin.cronin@chromium.org
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Change-Id: I9e9d4944519be30fdbc53c3fb3fbd4083e3b2785
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1632532
Commit-Queue: Patrick Monette <pmonette@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664940}
27 files changed