Revert of New method StatsObserver::OnCompleteReports, passing ownership. (patchset #2 id:20001 of https://codereview.webrtc.org/2584553002/ )

Reason for revert:
The new method doesn't work as intended.

It can't pass ownership, because the StatsReports is a vector of raw pointers to StatReport objects owned by the StatsCollector.

Original issue's description:
> New method StatsObserver::OnCompleteReports, passing ownership.
>
> The new name, OnCompleteReports rather than OnComplete, is needed
> because in C++ method lookup, overriding a method hides all otherwise
> inherited methods with the same name, even if they have a different
> signature. And here, the intention is that each subclass should
> override one or the other of the two methods, and inherit the method it
> doesn't override.
>
> This cl is a prerequisite for
> https://codereview.webrtc.org/2567143003/, because the Chrome glue
> code needs to retain the stats report after the OnComplete method has
> returned.
>
> Currently, Chrome makes a copy of the stats mapping (which breaks when
> changing ValuePtr from an rtc::linked_ptr to an std::unique_ptr). After
> this cl, Chrome can be fixed to take ownership and no longer needs to
> copy anything, unblocking cl 2567143003.
>
> BUG=webrtc:6424
>
> Review-Url: https://codereview.webrtc.org/2584553002
> Cr-Commit-Position: refs/heads/master@{#15708}
> Committed: https://chromium.googlesource.com/external/webrtc/+/b36ee8d498be2fa58fde3f3f3d69a74e4d3b817d

TBR=solenberg@webrtc.org,magjed@webrtc.org,tkchin@webrtc.org,hbos@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:6424

Review-Url: https://codereview.webrtc.org/2641783002
Cr-Commit-Position: refs/heads/master@{#16144}
5 files changed
tree: d166b2f3c858c5307c9b1a228d8292573cb70f68
  1. build_overrides/
  2. data/
  3. infra/
  4. ios/
  5. resources/
  6. tools-webrtc/
  7. webrtc/
  8. .clang-format
  9. .git-blame-ignore-revs
  10. .gitignore
  11. .gn
  12. AUTHORS
  13. BUILD.gn
  14. check_root_dir.py
  15. cleanup_links.py
  16. codereview.settings
  17. DEPS
  18. LICENSE
  19. license_template.txt
  20. LICENSE_THIRD_PARTY
  21. OWNERS
  22. PATENTS
  23. PRESUBMIT.py
  24. pylintrc
  25. README.md
  26. WATCHLISTS
README.md

WebRTC is a free, open software project that provides browsers and mobile applications with Real-Time Communications (RTC) capabilities via simple APIs. The WebRTC components have been optimized to best serve this purpose.

Our mission: To enable rich, high-quality RTC applications to be developed for the browser, mobile platforms, and IoT devices, and allow them all to communicate via a common set of protocols.

The WebRTC initiative is a project supported by Google, Mozilla and Opera, amongst others. This page is maintained by the Google Chrome team.

Development

See http://www.webrtc.org/native-code/development for instructions on how to get started developing with the native code.

More info