Move texture registry ownership to platform view (#4348)

* Move texture registry ownership to platform view

This enables the texture registry to survive activity pause on Android.

shell/gpu/gpu_rasterizer.cc

@@ -161,4 +161,8 @@ void GPURasterizer::NotifyNextFrameOnce() {
   }
 }
 
+void GPURasterizer::SetTextureRegistry(flow::TextureRegistry* textureRegistry) {
+  compositor_context_.SetTextureRegistry(std::move(textureRegistry));
+}
+
 }  // namespace shell

shell/gpu/gpu_rasterizer.h

@@ -42,6 +42,8 @@ class GPURasterizer : public Rasterizer {
   // Set a callback to be called once when the next frame is drawn.
   void AddNextFrameCallback(fxl::Closure nextFrameCallback) override;
 
+  void SetTextureRegistry(flow::TextureRegistry* textureRegistry) override;
+
  private:
   std::unique_ptr<Surface> surface_;
   flow::CompositorContext compositor_context_;