Rename paint data structures

cc/paint/README.md

+# cc/paint
+
+This document gives an overview of the paint component of cc.
+
+[TOC]
+
+## Overview
+
+cc/paint is a replacement for SkPicture/SkCanvas/SkPaint
+recording data structures throughout the Chrome codebase, primarily
+meaning Blink and ui.  The reason for a separate data structure
+is to change the way that recordings are stored to improve
+transport and recording performance.
+
+Skia will still be the ultimate backend for raster, and so
+any place in code that still wants to raster directly (either
+for test expectations or to create an SkImage, for example)
+should continue to use Skia data structures.
+
+## Dependencies
+
+As this component is used in both Blink and ui, it should only include
+files that Blink is also allowed to depend on.  This means not including
+base/ or using std data structures publicly.
+
+This is why cc/paint uses sk_sp reference counting at the moment as
+a compromise between Blink and chrome style.