cc: Clean up naming of paint-related identifiers

cc/paint/paint_flags.h

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_PAINT_PAINT_FLAGS_H_
 #define CC_PAINT_PAINT_FLAGS_H_
 
 #include "third_party/skia/include/core/SkPaint.h"
 
 namespace cc {
 
 using PaintFlags = SkPaint;
 
-inline const SkPaint& ToSkPaint(const PaintFlags& paint) {
-  return paint;
+inline const SkPaint& ToSkPaint(const PaintFlags& flags) {
+  return flags;
 }
 
 }  // namespace cc
 
 #endif  // CC_PAINT_PAINT_FLAGS_H_