WIP RasterCanvasLayerAllocator

src/core/SkBitmapDevice.cpp

Index: src/core/SkBitmapDevice.cpp
diff --git a/src/core/SkBitmapDevice.cpp b/src/core/SkBitmapDevice.cpp
index 119a434cc9cde8a5077a18702ba2394e67a183f8..c7bf98f1cd3b6c77d381173a4064c486f73047da 100644
--- a/src/core/SkBitmapDevice.cpp
+++ b/src/core/SkBitmapDevice.cpp
@@ -15,6 +15,7 @@
 #include "SkPath.h"
 #include "SkPixelRef.h"
 #include "SkPixmap.h"
+#include "SkRasterCanvasLayerAllocator.h"
 #include "SkShader.h"
 #include "SkSurface.h"
 #include "SkXfermode.h"
@@ -129,9 +130,22 @@ void SkBitmapDevice::replaceBitmapBackendForRasterSurface(const SkBitmap& bm) {
     fBitmap.lockPixels();
 }
 
-SkBaseDevice* SkBitmapDevice::onCreateDevice(const CreateInfo& cinfo, const SkPaint*) {
+SkBaseDevice* SkBitmapDevice::onCreateDevice(const CreateInfo& cinfo, const SkPaint*,
+                                             SkRasterCanvasLayerAllocator* alloc) {
     const SkSurfaceProps surfaceProps(this->surfaceProps().flags(), cinfo.fPixelGeometry);
-    return SkBitmapDevice::Create(cinfo.fInfo, surfaceProps);
+    SkBitmapDevice* dev = nullptr;
+    if (alloc) {
+        SkBitmap bitmap;
+        size_t rowBytes;
+        void* layer = alloc->allocateLayer(cinfo.fInfo, &rowBytes);
+        if (layer &&
+            bitmap.installPixels(cinfo.fInfo, layer, rowBytes)) {
+            dev = new SkBitmapDevice(bitmap);
+        }
+    } else {
+        dev = SkBitmapDevice::Create(cinfo.fInfo, surfaceProps);
+    }
+    return dev;
 }
 
 const SkBitmap& SkBitmapDevice::onAccessBitmap() {