Bug 1699588 - Enable external compositing of SurfaceTexture with sw-wr r=gfx-reviewers,lsalzman

SurfaceTexture handling for external compositing is implemented in RenderCompositorOGLSWGL::HandleExternalImage().

Differential Revision: https://phabricator.services.mozilla.com/D115338

gfx/layers/opengl/TextureHostOGL.cpp

@@ -732,6 +732,11 @@ void SurfaceTextureHost::PushDisplayItems(wr::DisplayListBuilder& aBuilder,
   }
 }
 
+bool SurfaceTextureHost::SupportsExternalCompositing(
+    WebRenderBackend aBackend) {
+  return aBackend == WebRenderBackend::SOFTWARE;
+}
+
 ////////////////////////////////////////////////////////////////////////
 // AndroidHardwareBufferTextureHost
 

gfx/layers/opengl/TextureHostOGL.h

@@ -452,6 +452,8 @@ class SurfaceTextureHost : public TextureHost {
                         const Range<wr::ImageKey>& aImageKeys,
                         PushDisplayItemFlagSet aFlags) override;
 
+  bool SupportsExternalCompositing(WebRenderBackend aBackend) override;
+
   // gecko does not need deferred deletion with WebRender
   // GPU/hardware task end could be checked by android fence.
   // SurfaceTexture uses android fence internally,