Revert of Add non-inline SkRTreeFactory constructor to fix clang-cl (patchset #2...

Revert of Add non-inline SkRTreeFactory constructor to fix clang-cl (patchset #2 id:20001 of https://codereview.chromium.org/1676833002/ )

Reason for revert:
This workaround should no longer be needed, per comment#16 from
thakis@ on the original CL.

Original issue's description:
> Add non-inline SkRTreeFactory constructor to fix clang-cl
>
> When Chromium is switched to build with VS 2015 that switches clang-cl
> to build in -fmsc-version=1900 mode. This causes some changes in
> importing of constructors and vftables which leads to link errors in
> blink_platform.dll. Adding a non-inline constructor makes 1900 mode
> behave consistently with 1800 mode and avoids the link error.
>
> The root cause needs investigation but this will unblock the VS 2015
> switch.
>
> BUG=440500,498544
> GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1676833002
>
> Committed: https://skia.googlesource.com/skia/+/964eec67760196585954203ba625e440607f7e92

TBR=reed@google.com,bsalomon@google.com,mtklein@chromium.org,thakis@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=440500,498544

Review URL: https://codereview.chromium.org/1739363002