Extract shell methods from ApplicationImpl into a base class, and pass this to Initialize() instead.

components/filesystem/file_system_app.cc

Index: components/filesystem/file_system_app.cc
diff --git a/components/filesystem/file_system_app.cc b/components/filesystem/file_system_app.cc
index 662d2e2a3e328abc9b5dec06a6bc3bbbec705328..855ece40c7037ff01eefae5e188b8921b8574ce2 100644
--- a/components/filesystem/file_system_app.cc
+++ b/components/filesystem/file_system_app.cc
@@ -9,17 +9,18 @@
 #include "base/bind.h"
 #include "base/logging.h"
 #include "mojo/shell/public/cpp/application_connection.h"
-#include "mojo/shell/public/cpp/application_impl.h"
+#include "mojo/shell/public/cpp/shell.h"
 
 namespace filesystem {
 
-FileSystemApp::FileSystemApp() : app_(nullptr), in_shutdown_(false) {}
+FileSystemApp::FileSystemApp() : shell_(nullptr), in_shutdown_(false) {}
 
 FileSystemApp::~FileSystemApp() {}
 
-void FileSystemApp::Initialize(mojo::ApplicationImpl* app) {
-  app_ = app;
-  tracing_.Initialize(app);
+void FileSystemApp::Initialize(mojo::Shell* shell, const std::string& url,
+                               uint32_t id) {
+  shell_ = shell;
+  tracing_.Initialize(shell, url);
 }
 
 bool FileSystemApp::AcceptConnection(
@@ -70,7 +71,7 @@ void FileSystemApp::OnDirectoryConnectionError(DirectoryImpl* directory) {
       if (in_shutdown_ && client_mapping_.empty()) {
         // We just cleared the last directory after our shell connection went
         // away. Time to shut ourselves down.
-        app_->Quit();
+        shell_->Quit();
       }
 
       return;