[Windows] Decouple the GL context from the view

shell/platform/windows/flutter_windows_engine.cc

@@ -53,17 +53,17 @@ FlutterRendererConfig GetOpenGLRendererConfig() {
   config.open_gl.struct_size = sizeof(config.open_gl);
   config.open_gl.make_current = [](void* user_data) -> bool {
     auto host = static_cast<FlutterWindowsEngine*>(user_data);
-    if (!host->view()) {
+    if (!host->surface_manager()) {
       return false;
     }
-    return host->view()->MakeCurrent();
+    return host->surface_manager()->MakeCurrent();
   };
   config.open_gl.clear_current = [](void* user_data) -> bool {
     auto host = static_cast<FlutterWindowsEngine*>(user_data);
-    if (!host->view()) {
+    if (!host->surface_manager()) {
       return false;
     }
-    return host->view()->ClearContext();
+    return host->surface_manager()->ClearContext();
   };
   config.open_gl.present = [](void* user_data) -> bool {
     auto host = static_cast<FlutterWindowsEngine*>(user_data);
@@ -89,10 +89,10 @@ FlutterRendererConfig GetOpenGLRendererConfig() {
   };
   config.open_gl.make_resource_current = [](void* user_data) -> bool {
     auto host = static_cast<FlutterWindowsEngine*>(user_data);
-    if (!host->view()) {
+    if (!host->surface_manager()) {
       return false;
     }
-    return host->view()->MakeResourceCurrent();
+    return host->surface_manager()->MakeResourceCurrent();
   };
   config.open_gl.gl_external_texture_frame_callback =
       [](void* user_data, int64_t texture_id, size_t width, size_t height,

shell/platform/windows/flutter_windows_view.cc

@@ -535,18 +535,6 @@ void FlutterWindowsView::SendPointerEventWithData(
   }
 }
 
-bool FlutterWindowsView::MakeCurrent() {
-  return engine_->surface_manager()->MakeCurrent();
-}
-
-bool FlutterWindowsView::MakeResourceCurrent() {
-  return engine_->surface_manager()->MakeResourceCurrent();
-}
-
-bool FlutterWindowsView::ClearContext() {
-  return engine_->surface_manager()->ClearContext();
-}
-
 bool FlutterWindowsView::SwapBuffers() {
   // Called on an engine-controlled (non-platform) thread.
   std::unique_lock<std::mutex> lock(resize_mutex_);

shell/platform/windows/flutter_windows_view.h

@@ -65,11 +65,12 @@ class FlutterWindowsView : public WindowBindingHandlerDelegate {
   // Tells the engine to generate a new frame
   void ForceRedraw();
 
-  // Callbacks for clearing context, settings context and swapping buffers,
-  // these are typically called on an engine-controlled (non-platform) thread.
-  bool ClearContext();
-  bool MakeCurrent();
-  bool MakeResourceCurrent();
+  // Swap the view's surface buffers. Must be called on the engine's raster
+  // thread. Returns true if the buffers were swapped.
+  //
+  // If the view is resizing, this returns false if the frame is not the target
+  // size. Otherwise, it unblocks the platform thread and blocks the raster
+  // thread until the v-blank.
   bool SwapBuffers();
 
   // Callback for presenting a software bitmap.