8354 Rename threshold to access_threshold (cla: yes)

8355 Create ddc summary file and precompiled sdk (cla: yes)

8358 Allow per-platform customization of the default Skia font manager (cla: yes)

8359 update buildroot dep for PR #227 (cla: yes)

8360 Remove old Fuchsia external mem,sem extensions (cla: yes)

8362 Ensure OpacityLayer to have a single child (cla: yes)

8368 libtxt: track the start and end x positions of glyph blobs for more accurate rendering of text decorations (cla: yes)

8369 GN Format all files in the engine. (cla: yes)

8371 Add a GN format presubmit. (cla: yes)