use SkColorType instead of (deprecated) SkBitmap::Config for copyTo

cc/resources/bitmap_content_layer_updater.cc

Index: cc/resources/bitmap_content_layer_updater.cc
diff --git a/cc/resources/bitmap_content_layer_updater.cc b/cc/resources/bitmap_content_layer_updater.cc
index 6f2332bf84a2cbe581c05c5b1584dd5986522a45..6f7cd010579ae129f3c93ad5f20d7a60d66aa3e2 100644
--- a/cc/resources/bitmap_content_layer_updater.cc
+++ b/cc/resources/bitmap_content_layer_updater.cc
@@ -64,11 +64,8 @@ void BitmapContentLayerUpdater::PrepareToUpdate(
     devtools_instrumentation::ScopedLayerTask paint_setup(
         devtools_instrumentation::kPaintSetup, layer_id_);
     canvas_size_ = content_rect.size();
-    bitmap_backing_.setConfig(
-        SkBitmap::kARGB_8888_Config,
-        canvas_size_.width(), canvas_size_.height(),
-        0, layer_is_opaque_ ? kOpaque_SkAlphaType : kPremul_SkAlphaType);
-    bitmap_backing_.allocPixels();
+    bitmap_backing_.allocN32Pixels(
+        canvas_size_.width(), canvas_size_.height(), layer_is_opaque_);
     canvas_ = skia::AdoptRef(new SkCanvas(bitmap_backing_));
   }