Move fileSystem API FilePicker class to own file

chrome/browser/extensions/api/file_system/file_system_api.h

Index: chrome/browser/extensions/api/file_system/file_system_api.h
diff --git a/chrome/browser/extensions/api/file_system/file_system_api.h b/chrome/browser/extensions/api/file_system/file_system_api.h
index f65f4183c3267efacc3c3a84a61ff4f836364c12..d43a8e298394a136dfac0020e77194c3c4873d14 100644
--- a/chrome/browser/extensions/api/file_system/file_system_api.h
+++ b/chrome/browser/extensions/api/file_system/file_system_api.h
@@ -25,6 +25,10 @@
 #include "chrome/browser/extensions/api/file_system/consent_provider.h"
 #endif
 
+namespace content {
+class WebContents;
+}  // namespace content
+
 namespace extensions {
 class ExtensionPrefs;
 
@@ -155,8 +159,6 @@ class FileSystemChooseEntryFunction : public FileSystemEntryFunction {
                               base::FilePath::StringType* suggested_extension);
 
  protected:
-  class FilePicker;
-
   ~FileSystemChooseEntryFunction() override {}
   bool RunAsync() override;
   void ShowPicker(const ui::SelectFileDialog::FileTypeInfo& file_type_info,
@@ -171,7 +173,7 @@ class FileSystemChooseEntryFunction : public FileSystemEntryFunction {
       bool is_path_non_native_directory);
 
   // FilesSelected and FileSelectionCanceled are called by the file picker.
-  void FilesSelected(const std::vector<base::FilePath>& path);
+  void FilesSelected(const std::vector<base::FilePath>& paths);
   void FileSelectionCanceled();
 
   // Check if the chosen directory is or is an ancestor of a sensitive