[CrOS Cellular] Convert OtaActivator's BindingSet to a single Binding.

OtaActivator objects are meant to be single-use with a single binding,
so there was never a need to use a BindingSet here.

Bug: 961084
Change-Id: I4b60cc7c556faed5acaec80a211aae1f22cf117d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1641549Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Auto-Submit: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666087}

chromeos/services/cellular_setup/ota_activator.cc

@@ -11,13 +11,16 @@ namespace chromeos {
 namespace cellular_setup {
 
 OtaActivator::OtaActivator(base::OnceClosure on_finished_callback)
-    : on_finished_callback_(std::move(on_finished_callback)) {}
+    : on_finished_callback_(std::move(on_finished_callback)), binding_(this) {}
 
 OtaActivator::~OtaActivator() = default;
 
 mojom::CarrierPortalHandlerPtr OtaActivator::GenerateInterfacePtr() {
+  // Only one InterfacePtr should be created per instance.
+  DCHECK(!binding_);
+
   mojom::CarrierPortalHandlerPtr interface_ptr;
-  bindings_.AddBinding(this, mojo::MakeRequest(&interface_ptr));
+  binding_.Bind(mojo::MakeRequest(&interface_ptr));
   return interface_ptr;
 }
 

chromeos/services/cellular_setup/ota_activator.h

@@ -8,7 +8,7 @@
 #include "base/callback.h"
 #include "base/macros.h"
 #include "chromeos/services/cellular_setup/public/mojom/cellular_setup.mojom.h"
-#include "mojo/public/cpp/bindings/binding_set.h"
+#include "mojo/public/cpp/bindings/binding.h"
 
 namespace chromeos {
 
@@ -23,6 +23,9 @@ class OtaActivator : public mojom::CarrierPortalHandler {
  public:
   ~OtaActivator() override;
 
+  // Generates an InterfacePtr bound to this instance. Only one InterfacePtr may
+  // be bound to a single OtaActivator instance, so this function can only be
+  // called once.
   mojom::CarrierPortalHandlerPtr GenerateInterfacePtr();
 
  protected:
@@ -31,7 +34,7 @@ class OtaActivator : public mojom::CarrierPortalHandler {
   void InvokeOnFinishedCallback();
 
   base::OnceClosure on_finished_callback_;
-  mojo::BindingSet<mojom::CarrierPortalHandler> bindings_;
+  mojo::Binding<mojom::CarrierPortalHandler> binding_;
 
   DISALLOW_COPY_AND_ASSIGN(OtaActivator);
 };