Use the given task runner for AssociatedInterfaceProvider::GetInterface.

[Context]
This is a part of an effort to achieve MBI. We want to avoid per-thread task runner as much as possible.

[Previous code]
AssociatedInterfaceProvider::GetInterface was using per-thread default task runner because task_runner was not specified.

[What this CL does]
Use the given task runner for AssociatedInterfaceProvider::GetInterface instead of per-thread task runner

[Rlated stack trace]
base::SequencedTaskRunnerHandle::Get()
mojo::internal::GetTaskRunnerToUseFromUserProvidedTaskRunner()
mojo::internal::AssociatedInterfacePtrStateBase::Bind()
mojo::internal::AssociatedInterfacePtrState<>::Bind()
mojo::AssociatedRemote<>::Bind()
mojo::AssociatedRemote<>::BindNewEndpointAndPassReceiver()
mojo::AssociatedRemote<>::BindNewEndpointAndPassReceiver()
blink::AssociatedInterfaceProvider::GetInterface<>()
content::RenderFrameImpl::GetFrameHost()
content::(anonymous namespace)::ResourceLoadCompleted()
content::NotifyResourceLoadCompleted()
content::NavigationBodyLoader::NotifyCompletionIfAppropriate()
content::NavigationBodyLoader::OnComplete()
network::mojom::URLLoaderClientStubDispatch::Accept()
network::mojom::URLLoaderClientStub<>::Accept()

Bug: 1105403
Change-Id: I20d3e2a7e1ba638a94d30e33d964d8df5f8fd418
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2462857Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Dominic Farolino <dom@chromium.org>
Commit-Queue: Minoru Chikamune <chikamune@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816900}

third_party/blink/public/common/associated_interfaces/associated_interface_provider.h

@@ -65,7 +65,7 @@ class BLINK_COMMON_EXPORT AssociatedInterfaceProvider {
 
   template <typename Interface>
   void GetInterface(mojo::AssociatedRemote<Interface>* remote) {
-    GetInterface(remote->BindNewEndpointAndPassReceiver());
+    GetInterface(remote->BindNewEndpointAndPassReceiver(task_runner_));
   }
 
   void OverrideBinderForTesting(