a6917332f8
Previously, if `layout_data` was not nil, we failed to `CFRelease` `source`. However, if `layout_data` was nil, we dif free source, then immediately set it to a new CoreFoundation object, which we then failed to free. We now use `fml::CFRef` which just does the right thing. Finally, we were returning `(__brdige_transfer)CFRetain(layout_data)` but `__bridge_transfer` releases the transferred object at the end of the enclosing expression, so this is equivalent to `(__bridge)layout_data`, which is what we now do. No tests since this is a refactor with no semantic changes, other than fixing an internal leak. [C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style