Include Semantics Node in debugDumpRenderTree, if available (#10338)
Include Semantics Node in debugDumpRenderTree, if available (#10338)

Makes debugging semantics easier (e.g. which RenderObject has semantics, where is a SemanticNode seen in the semantic tree comming from, etc).

It's only printed if accessibility is turned on.
Hixie/flutter,turnidge/flutter,Hixie/flutter,Hixie/flutter,flutter/flutter,turnidge/flutter,tvolkert/flutter,cbracken/flutter,flutter/flutter,cbracken/flutter,Hixie/flutter,flutter/flutter,cbracken/flutter,tvolkert/flutter,flutter/flutter,cbracken/flutter,cbracken/flutter,turnidge/flutter,cbracken/flutter,cbracken/flutter,flutter/flutter,tvolkert/flutter,flutter/flutter,Hixie/flutter,turnidge/flutter,tvolkert/flutter,tvolkert/flutter,Hixie/flutter,tvolkert/flutter,flutter/flutter,Hixie/flutter,Hixie/flutter,flutter/flutter,tvolkert/flutter,flutter/flutter,tvolkert/flutter,turnidge/flutter,cbracken/flutter,tvolkert/flutter,Hixie/flutter,cbracken/flutter,Hixie/flutter,flutter/flutter,tvolkert/flutter,cbracken/flutter