WIP RasterCanvasLayerAllocator experiment 2

skia/ext/layer_allocator_win.h

Index: skia/ext/layer_allocator_win.h
diff --git a/skia/ext/layer_allocator_win.h b/skia/ext/layer_allocator_win.h
new file mode 100644
index 0000000000000000000000000000000000000000..46da090ab4e9f2304b75bbcb962e427b7b17291d
--- /dev/null
+++ b/skia/ext/layer_allocator_win.h
@@ -0,0 +1,49 @@
+// Copyright 2016 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 SKIA_EXT_LAYER_ALLOCATOR_WIN_H_
+#define SKIA_EXT_LAYER_ALLOCATOR_WIN_H_
+
+#include "skia/ext/platform_surface.h"
+
+#include "third_party/skia/include/core/SkRasterCanvasLayerAllocator.h"
+
+#include <unordered_map>
+
+namespace skia {
+
+/*
+ * On Windows, a PlatformCanvas is backed by a CreateDIBSection()-allocated
+ * bitmap; a PlatformSurface is an HDC.
+ */
+class LayerAllocator : public SkRasterCanvasLayerAllocator {
+ public:
+  LayerAllocator();
+  ~LayerAllocator() override;
+
+  /// Returns HDC.
+  void* getNativeContext(void* buffer,
+                         const SkMatrix& transform,
+                         const SkIRect& clip_bounds) override;
+
+ protected:
+  /// Expects a HANDLE to a Windows shared section as (optional) initialData.
+  /// Returns the data pointer from an HBITMAP.
+  /// |deallocator| will ...() and ...()
+  /// the layer.
+  void* allocateLayer(const SkImageInfo& info, size_t* rowBytes,
+                      void (**deallocator)(void*),
+                      void** deallocatorPayload,
+                      void* initialData) override;
+
+ private:
+  typedef std::unordered_map<void*, HDC> context_map_t;
+  context_map_t contexts_;
+
+ friend class BitmapPlatformDevice;
+};
+
+}
+
+#endif  // SKIA_EXT_LAYER_ALLOCATOR_WIN_H_