Move content's shell connections to the IO thread

services/shell/public/cpp/shell_connection.h

Index: services/shell/public/cpp/shell_connection.h
diff --git a/services/shell/public/cpp/shell_connection.h b/services/shell/public/cpp/shell_connection.h
index 59ed8f2bb944eb43403c0af7c7fccb648b550e9b..458d22dc894ed8db5326efb93a2d9dbf28fa99d3 100644
--- a/services/shell/public/cpp/shell_connection.h
+++ b/services/shell/public/cpp/shell_connection.h
@@ -11,9 +11,9 @@
 
 #include "base/callback.h"
 #include "base/macros.h"
-#include "base/memory/scoped_vector.h"
 #include "mojo/public/cpp/bindings/binding.h"
 #include "mojo/public/cpp/system/core.h"
+#include "services/shell/public/cpp/connector.h"
 #include "services/shell/public/cpp/shell_client.h"
 #include "services/shell/public/interfaces/connector.mojom.h"
 #include "services/shell/public/interfaces/shell_client.mojom.h"
@@ -46,9 +46,13 @@ class ShellConnection : public mojom::ShellClient {
   // Creates a new ShellConnection bound to |request|. This connection may be
   // used immediately to make outgoing connections via connector().  Does not
   // take ownership of |client|, which must remain valid for the lifetime of
-  // ShellConnection.
+  // ShellConnection. If either |connector| or |connector_request| is non-null
+  // both must be non-null. If both are null, the connection will create its own
+  // Connector and request to pass to the shell on initialization.
   ShellConnection(shell::ShellClient* client,
-                  mojom::ShellClientRequest request);
+                  mojom::ShellClientRequest request,
+                  std::unique_ptr<Connector> connector = nullptr,
+                  mojom::ConnectorRequest connector_request = nullptr);
 
   ~ShellConnection() override;
 
@@ -85,7 +89,7 @@ class ShellConnection : public mojom::ShellClient {
 
   // We track the lifetime of incoming connection registries as it more
   // convenient for the client.
-  ScopedVector<Connection> incoming_connections_;
+  std::vector<std::unique_ptr<Connection>> incoming_connections_;
 
   // A pending Connector request which will eventually be passed to the shell.
   mojom::ConnectorRequest pending_connector_request_;