removed bpp (it can be calculated)

fixed buffer size calculation (we actually send the whole image, not just the dirty part)
removed the unnecessary resets and const
now we use Copy instead of New

atom/browser/api/atom_api_web_contents.cc

@@ -1345,16 +1345,15 @@ bool WebContents::IsOffScreen() const {
 
 void WebContents::OnPaint(const gfx::Rect& dirty_rect,
                           const gfx::Size& bitmap_size,
-                          const int pixel_size,
+                          int pixel_size,
                           void* bitmap_pixels) {
-  v8::MaybeLocal<v8::Object> buffer = node::Buffer::New(
+  v8::MaybeLocal<v8::Object> buffer = node::Buffer::Copy(
       isolate(), reinterpret_cast<char*>(bitmap_pixels),
-      pixel_size * dirty_rect.width() * dirty_rect.height());
+      pixel_size * bitmap_size.width() * bitmap_size.height());
 
   mate::Dictionary dict = mate::Dictionary::CreateEmpty(isolate());
   dict.Set("width", bitmap_size.width());
   dict.Set("height", bitmap_size.height());
-  dict.Set("bytesPerPixel", pixel_size);
 
   if (!buffer.IsEmpty())
     Emit("paint", dirty_rect, buffer.ToLocalChecked(), dict);
@@ -1367,8 +1366,8 @@ void WebContents::StartPainting() {
   auto* osr_rwhv = static_cast<OffScreenRenderWidgetHostView*>(
       web_contents()->GetRenderWidgetHostView());
   if (osr_rwhv) {
-    osr_rwhv->SetPainting(true);
     osr_rwhv->Show();
+    osr_rwhv->SetPainting(true);
   }
 }
 

atom/browser/osr/osr_render_widget_host_view.cc

@@ -379,13 +379,6 @@ OffScreenRenderWidgetHostView::~OffScreenRenderWidgetHostView() {
 #if defined(OS_MACOSX)
   DestroyPlatformWidget();
 #endif
-
-  if (copy_frame_generator_.get())
-    copy_frame_generator_.reset(nullptr);
-
-  delegated_frame_host_.reset(nullptr);
-  compositor_.reset(nullptr);
-  root_layer_.reset(nullptr);
 }
 
 void OffScreenRenderWidgetHostView::OnBeginFrameTimerTick() {