mandoline filesystem: add a sqlite3 vfs to proxy filesystem usage.

components/filesystem/directory_impl.cc

Index: components/filesystem/directory_impl.cc
diff --git a/components/filesystem/directory_impl.cc b/components/filesystem/directory_impl.cc
index fca0a212afba2ae9ec9ea4ed669dada3e611642e..3d2a758e518f7bd7e8547ca0b8348fc6bfa97db4 100644
--- a/components/filesystem/directory_impl.cc
+++ b/components/filesystem/directory_impl.cc
@@ -165,4 +165,27 @@ void DirectoryImpl::Delete(const mojo::String& raw_path,
   callback.Run(FILE_ERROR_OK);
 }
 
+void DirectoryImpl::Exists(const mojo::String& raw_path,
+                           const ExistsCallback& callback) {
+  base::FilePath path;
+  if (FileError error = ValidatePath(raw_path, directory_path_, &path)) {
+    callback.Run(error, false);
+    return;
+  }
+
+  bool exists = base::PathExists(path);
+  callback.Run(FILE_ERROR_OK, exists);
+}
+
+void DirectoryImpl::IsWritable(const mojo::String& raw_path,
+                               const IsWritableCallback& callback) {
+  base::FilePath path;
+  if (FileError error = ValidatePath(raw_path, directory_path_, &path)) {
+    callback.Run(error, false);
+    return;
+  }
+
+  callback.Run(FILE_ERROR_OK, base::PathIsWritable(path));
+}
+
 }  // namespace filesystem