The renderer/platform/ directory contains lower-level, self-contained abstractions that core/ and modules/ can depend on.
See renderer/README.md for more about the relationship of platform/ to core/ and modules/.
Here is a non-exhaustive list of some major things in renderer/platform/:
bindings/ contains reusable components for the V8-DOM bindings layerexported/ implements some classes in the Blink Public API which are declared in public/platform/, including blink::Platform which initializes Blinkfonts/ and text/ contain Blink's font and text stackgraphics/ contains graphics support code including the Blink compositing algorithmheap/ contains the Blink GC system (a.k.a. Oilpan)loader/ contains functionality for loading resources from the networkscheduler/ contains the Blink Scheduler which coordinates task execution in renderer processeswidget/ handles input and compositing; WidgetBase owns LayerTreeView which wraps cc/ (the renderer compositor)wtf/ (Web Template Framework) is a library of containers and other basic functionalities