Add pattern matchers for SkRecord

src/record/SkRecordTraits.h

-#include "SkRecords.h"
-#include "SkTLogic.h"
-
-// Type traits that are useful for working with SkRecords.
-
-namespace SkRecords {
-
-namespace {
-
-// Abstracts away whether the T is optional or not.
-template <typename T> const T* as_ptr(const SkRecords::Optional<T>& x) { return x; }
-template <typename T> const T* as_ptr(const T& x) { return &x; }
-
-}  // namespace
-
-// Gets the paint from any command that may have one.
-template <typename Command> const SkPaint* GetPaint(const Command& x) { return as_ptr(x.paint); }
-
-// Have a paint?  You are a draw command!
-template <typename Command> struct IsDraw {
-    SK_CREATE_MEMBER_DETECTOR(paint);
-    static const bool value = HasMember_paint<Command>::value;
-};
-
-// Have a clip op?  You are a clip command.
-template <typename Command> struct IsClip {
-    SK_CREATE_MEMBER_DETECTOR(op);
-    static const bool value = HasMember_op<Command>::value;
-};
-
-}  // namespace SkRecords