Another stab at MTLRenderCommandEncoder memory leak.

Allocating the MTLRenderCommandEncoder within a separate method seems
to add an unwanted retain, which leaves the refCnt stuck at 1 even
when we set the pointer to nil (the __strong keyword was a red herring).
Allocating and setting to nil within the same method seems to give the
right number of retain/release pairs.

Bug: skia:8243
Change-Id: Ic9a7180915e2753565d706b42d4d07eedb42519e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/198175
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
2 files changed