Consolidate Windows bitmap and DC code

skia/ext/skia_utils_win.h

Index: skia/ext/skia_utils_win.h
diff --git a/skia/ext/skia_utils_win.h b/skia/ext/skia_utils_win.h
index b116efe19e2625cb896bcbd33f93d11e59266407..01a66f5d3526d11c67241f735616cc6e61ae16d1 100644
--- a/skia/ext/skia_utils_win.h
+++ b/skia/ext/skia_utils_win.h
@@ -5,7 +5,9 @@
 #ifndef SKIA_EXT_SKIA_UTILS_WIN_H_
 #define SKIA_EXT_SKIA_UTILS_WIN_H_
 
+#include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkColor.h"
+#include "third_party/skia/include/core/SkRefCnt.h"
 
 #include "build/build_config.h"
 #include <windows.h>
@@ -13,6 +15,7 @@
 struct SkIRect;
 struct SkPoint;
 struct SkRect;
+class SkSurface;
 typedef unsigned long DWORD;
 typedef DWORD COLORREF;
 typedef struct tagPOINT POINT;
@@ -49,6 +52,21 @@ SK_API COLORREF SkColorToCOLORREF(SkColor color);
 // Initializes the default settings and colors in a device context.
 SK_API void InitializeDC(HDC context);
 
+// Creates a surface writing to the pixels backing the HDC's bitmap.
+// Returns nullptr on error.
+SK_API sk_sp<SkSurface> MapPlatformSurface(HDC context);
+
+// Creates a bitmap backed by the same pixels backing the HDC's bitmap.
+// Returns an empty bitmap on error.
+SK_API SkBitmap MapPlatformBitmap(HDC context);
+
+// Creates an offscreen HDC suitable for writing to via MapPlatformSurface().
+// Caller is responsible for calling DeleteDC() when done.
+SK_API HDC CreateOffscreenSurface(int width, int height);
+
+// Fills in a BITMAPINFOHEADER structure given the bitmap's size.
+SK_API void CreateBitmapHeader(int width, int height, BITMAPINFOHEADER* hdr);
+
 }  // namespace skia
 
 #endif  // SKIA_EXT_SKIA_UTILS_WIN_H_