48539 Update BUG.md (cla: yes)

48541 Make ParentDataWidget usable with different ancestor RenderObjectWidget types (cla: yes, framework, waiting for tree to go green)

48547 Migrate TextTheme to 2018 APIs (cla: yes, d: examples, f: material design, framework, team, team: gallery, tool, waiting for tree to go green)

48548 [flutter_tools] Discover pubspec.yaml in parent directories (cla: yes, tool, waiting for tree to go green)

48575 Fixing AutomaticKeepAlive Docs (cla: yes, d: api docs, documentation, framework, waiting for tree to go green)

48582 Revert “Migrate some more integration tests to Android embedding v2” (cla: yes, team)