Add Protobuf support for cc/playback skia usage

cc/proto/skia_conversions.h

+// Copyright 2015 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_PROTO_SKIA_CONVERSIONS_H_
+#define CC_PROTO_SKIA_CONVERSIONS_H_
+
+#include "cc/base/cc_export.h"
+#include "cc/proto/skregion.pb.h"
+#include "cc/proto/skxfermode.pb.h"
+#include "third_party/skia/include/core/SkRegion.h"
+#include "third_party/skia/include/core/SkXfermode.h"
+
+class SkRegion;
+class SkRRect;
+class SkXferMode;
+
+namespace cc {
+
+namespace proto {
+class SkRRect;
+}
+
+CC_EXPORT SkRegion::Op SkRegionOpFromProto(proto::SkRegion::Op op);
+CC_EXPORT proto::SkRegion::Op SkRegionOpToProto(SkRegion::Op op);
+
+CC_EXPORT SkXfermode::Mode SkXfermodeModeFromProto(
+    proto::SkXfermode::Mode mode);
+CC_EXPORT proto::SkXfermode::Mode SkXfermodeModeToProto(SkXfermode::Mode mode);
+
+CC_EXPORT void SkRRectToProto(const SkRRect& rect, proto::SkRRect* proto);

[vmpstr, 2015/10/21 21:58:53]

Why the inconsistency with the rest? The rest return the value instead of taking
it my ptr.

[David Trainor- moved to gerrit, 2015/10/23 15:40:51]

Ah because the general use case for building proto messages is something like
the following:

SkRRectToProto(rect, message->mutable_skrrect());

For the other types they're just basic data, so there's nothing to build into. 
This format is actually what most of the gfx_conversions.h functions look like.

+CC_EXPORT SkRRect ProtoToSkRRect(const proto::SkRRect& proto);
+
+}  // namespace cc
+
+#endif  // CC_PROTO_SKIA_CONVERSIONS_H_