[flutter_runner] Rename outgoing 'public' to 'svc'.

This is the topaz counterpart to
https://fuchsia-review.googlesource.com/c/fuchsia/+/277254.

This is a backwards-incompatible ABI change that will be landed together
with that CL. All clients have been migrated to be compatible with the
new ABI.

Change-Id: I07bb460ce3c6971eb671874db1f90e8c4906e656

Ported from Topaz tree.

Author: cbracken

shell/platform/fuchsia/flutter/component.cc

@@ -159,7 +159,7 @@ Application::Application(
   // flutter_public_dir is only accessed once we receive OnOpen Event.
   // That will prevent FL-175 for public directory
   auto request = flutter_public_dir.NewRequest().TakeChannel();
-  fdio_service_connect_at(directory_ptr_.channel().get(), "public",
+  fdio_service_connect_at(directory_ptr_.channel().get(), "svc",
                           request.release());
 
   auto service_provider_dir = std::make_unique<ServiceProviderDir>();
@@ -209,7 +209,7 @@ Application::Application(
                           std::move(channel)));
           }));
 
-  outgoing_dir_->AddEntry("public", std::move(service_provider_dir));
+  outgoing_dir_->AddEntry("svc", std::move(service_provider_dir));
 
   // Setup the application controller binding.
   if (application_controller_request) {

shell/platform/fuchsia/flutter/runner_context.cc

@@ -13,7 +13,7 @@ RunnerContext::RunnerContext(std::shared_ptr<sys::ServiceDirectory> svc,
       public_dir_(std::make_shared<vfs::PseudoDir>()),
       debug_dir_(std::make_shared<vfs::PseudoDir>()),
       ctrl_dir_(std::make_shared<vfs::PseudoDir>()) {
-  root_dir_->AddSharedEntry("public", public_dir_);
+  root_dir_->AddSharedEntry("svc", public_dir_);
   root_dir_->AddSharedEntry("debug", debug_dir_);
   root_dir_->AddSharedEntry("ctrl", ctrl_dir_);