cc: Remove the software compositing bool from PrepareTextureMailbox

cc/output/renderer_capabilities_impl.cc

Index: cc/output/renderer_capabilities_impl.cc
diff --git a/cc/output/renderer_capabilities_impl.cc b/cc/output/renderer_capabilities_impl.cc
index d66877c5a0a5642e935759e57d0df567fef67bb5..c4fe2c8ab318d89961d1416bada44907f3748386 100644
--- a/cc/output/renderer_capabilities_impl.cc
+++ b/cc/output/renderer_capabilities_impl.cc
@@ -9,9 +9,4 @@ namespace cc {
 RendererCapabilitiesImpl::RendererCapabilitiesImpl() = default;
 RendererCapabilitiesImpl::~RendererCapabilitiesImpl() = default;
 
-RendererCapabilities RendererCapabilitiesImpl::MainThreadCapabilities() const {
-  return RendererCapabilities(best_texture_format, max_texture_size,
-                              using_shared_memory_resources);
-}
-
 }  // namespace cc