Reland "Supports the new vsh-into-running-container syntax"

This is a reland of e9753daf

Original change's description:
> Supports the new vsh-into-running-container syntax
> 
> It is no longer necessary to use the run_container.sh script every time a
> container shell is needed. If the container is already running, vsh now allows
> "direct access".
> 
> Bug: 848447
> Change-Id: Ia9aeb120befd016386816cdd16fb3336b45426ff
> Reviewed-on: https://chromium-review.googlesource.com/1082055
> Reviewed-by: Timothy Loh <timloh@chromium.org>
> Commit-Queue: Nicholas Verne <nverne@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#563568}

Bug: 848447
Change-Id: I17c73a37a65a8316e62154556ee94fbc37dd703d
Reviewed-on: https://chromium-review.googlesource.com/1096875Reviewed-by: Timothy Loh <timloh@chromium.org>
Commit-Queue: Nicholas Verne <nverne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567068}

chrome/browser/chromeos/crostini/crostini_manager.cc

@@ -763,31 +763,28 @@ void CrostiniManager::LaunchContainerTerminal(
     Profile* profile,
     const std::string& vm_name,
     const std::string& container_name) {
-  std::string container_username = ContainerUserNameForProfile(profile);
   std::string vsh_crosh = base::StringPrintf(
       "chrome-extension://%s/html/crosh.html?command=vmshell",
       kCrostiniCroshBuiltinAppId);
   std::string vm_name_param = net::EscapeQueryParamValue(
       base::StringPrintf("--vm_name=%s", vm_name.c_str()), false);
+  std::string container_name_param = net::EscapeQueryParamValue(
+      base::StringPrintf("--target_container=%s", container_name.c_str()),
+      false);
   std::string owner_id_param = net::EscapeQueryParamValue(
       base::StringPrintf("--owner_id=%s",
                          CryptohomeIdForProfile(profile).c_str()),
       false);
-  std::string lxd_dir =
-      net::EscapeQueryParamValue("LXD_DIR=/mnt/stateful/lxd", false);
-  std::string lxd_conf =
-      net::EscapeQueryParamValue("LXD_CONF=/mnt/stateful/lxd_conf", false);
-  const extensions::Extension* crosh_extension =
-      extensions::ExtensionRegistry::Get(profile)->GetInstalledExtension(
-          kCrostiniCroshBuiltinAppId);
 
   std::vector<base::StringPiece> pieces = {
-      vsh_crosh,      vm_name_param, owner_id_param,     "--",
-      lxd_dir,        lxd_conf,      "run_container.sh", "--container_name",
-      container_name, "--user",      container_username, "--shell"};
+      vsh_crosh, vm_name_param, container_name_param, owner_id_param};
 
   GURL vsh_in_crosh_url(base::JoinString(pieces, "&args[]="));
 
+  const extensions::Extension* crosh_extension =
+      extensions::ExtensionRegistry::Get(profile)->GetInstalledExtension(
+          kCrostiniCroshBuiltinAppId);
+
   AppLaunchParams launch_params(
       profile, crosh_extension, extensions::LAUNCH_CONTAINER_WINDOW,
       WindowOpenDisposition::NEW_WINDOW, extensions::SOURCE_APP_LAUNCHER);