Create TextureBacking interface

This change introduces the TextureBacking interface that will be used
on PaintImage. This CL simply introduces the cc interface. Follow up
changes will introduce the blink-side implementation.

This is being done as part of the OOPR-Canvas2D project. For more info
about the project see the tracking bug here: crbug.com/1018894

Bug: 1031050
Change-Id: I844c441bea308507a541fd3e131159f7c1d16b8e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2131216Reviewed-by: Khushal <khushalsagar@chromium.org>
Commit-Queue: Jonah Chin <jochin@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#756058}

cc/paint/BUILD.gn

@@ -83,6 +83,7 @@ cc_component("paint") {
     "skottie_wrapper.h",
     "solid_color_analyzer.cc",
     "solid_color_analyzer.h",
+    "texture_backing.h",
     "transfer_cache_deserialize_helper.h",
     "transfer_cache_entry.cc",
     "transfer_cache_entry.h",

cc/paint/texture_backing.h

+// Copyright 2020 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_TEXTURE_BACKING_H_
+#define CC_PAINT_TEXTURE_BACKING_H_
+
+#include "cc/paint/paint_export.h"
+#include "third_party/skia/include/core/SkImage.h"
+#include "third_party/skia/include/core/SkImageInfo.h"
+
+namespace gpu {
+class Mailbox;
+}  // namespace gpu
+
+namespace cc {
+
+// Used for storing mailboxes in a PaintImage.
+// This class must be created, used and destroyed on the same thread.
+class CC_PAINT_EXPORT TextureBacking : public SkRefCnt {
+ public:
+  TextureBacking(const TextureBacking&) = delete;
+  ~TextureBacking() override = default;
+
+  TextureBacking& operator=(const TextureBacking&) = delete;
+
+  // Returns the metadata for the associated texture.
+  virtual const SkImageInfo& GetSkImageInfo() = 0;
+
+  // Returns the shared image mailbox backing for this texture.
+  virtual gpu::Mailbox GetMailbox() const = 0;
+
+  // Returns a texture backed SkImage wrapping the mailbox. Only supported if
+  // the context used to create this image has a valid GrContext.
+  virtual sk_sp<SkImage> GetAcceleratedSkImage() = 0;
+};
+
+}  // namespace cc
+
+#endif  // CC_PAINT_TEXTURE_BACKING_H_