Fix missing MakeCurrent in {Ensure,Discard}BackBuffer

{Ensure,Discard}BackBuffer uses skia to allocate memory for
SkiaOutputDeviceOffscreen and forwards it to GLSurface for
SkiaOutputDeviceGL. This requires context to be current.

Change-Id: Ia9b94dbf1b1c46b2ec1375a1d2aeceffabf1e9fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3107466
Reviewed-by: Peng Huang <penghuang@chromium.org>
Commit-Queue: Vasiliy Telezhnikov <vasilyt@chromium.org>
Cr-Commit-Position: refs/heads/main@{#913497}

components/viz/service/display_embedder/skia_output_surface_impl_on_gpu.cc

@@ -1910,4 +1910,19 @@ void SkiaOutputSurfaceImplOnGpu::InitDelegatedInkPointRendererReceiver(
   }
 }
 
+void SkiaOutputSurfaceImplOnGpu::EnsureBackbuffer() {
+  // We call GLSurface::SetBackbuffferAllocation in Ensure/Discard backbuffer,
+  // so technically need framebuffer. In reality no GLSurface implements it, but
+  // until it's removed we should keep true here.
+  MakeCurrent(/*need_framebuffer=*/true);
+  output_device_->EnsureBackbuffer();
+}
+void SkiaOutputSurfaceImplOnGpu::DiscardBackbuffer() {
+  // We call GLSurface::SetBackbuffferAllocation in Ensure/Discard backbuffer,
+  // so technically need framebuffer. In reality no GLSurface implements it, but
+  // until it's removed we should keep true here.
+  MakeCurrent(/*need_framebuffer=*/true);
+  output_device_->DiscardBackbuffer();
+}
+
 }  // namespace viz

components/viz/service/display_embedder/skia_output_surface_impl_on_gpu.h

@@ -147,8 +147,8 @@ class SkiaOutputSurfaceImplOnGpu
   // Runs |deferred_framebuffer_draw_closure| when SwapBuffers() or CopyOutput()
   // will not.
   void SwapBuffersSkipped();
-  void EnsureBackbuffer() { output_device_->EnsureBackbuffer(); }
-  void DiscardBackbuffer() { output_device_->DiscardBackbuffer(); }
+  void EnsureBackbuffer();
+  void DiscardBackbuffer();
   void FinishPaintRenderPass(const gpu::Mailbox& mailbox,
                              sk_sp<SkDeferredDisplayList> ddl,
                              std::vector<ImageContextImpl*> image_contexts,