Make StringPiece to be std::string_view alias

Bug: 237583012
Test: build + boot + UTs

Change-Id: I849831f4466d3b9c7ec842b75256e7fcba77a0c0
diff --git a/tools/aapt2/io/FileSystem.h b/tools/aapt2/io/FileSystem.h
index bc03b9b..0e798fc 100644
--- a/tools/aapt2/io/FileSystem.h
+++ b/tools/aapt2/io/FileSystem.h
@@ -60,12 +60,11 @@
   FileCollection() = default;
 
   /** Creates a file collection containing all files contained in the specified root directory. */
-  static std::unique_ptr<FileCollection> Create(const android::StringPiece& path,
-                                                std::string* outError);
+  static std::unique_ptr<FileCollection> Create(android::StringPiece path, std::string* outError);
 
   // Adds a file located at path. Returns the IFile representation of that file.
-  IFile* InsertFile(const android::StringPiece& path);
-  IFile* FindFile(const android::StringPiece& path) override;
+  IFile* InsertFile(android::StringPiece path);
+  IFile* FindFile(android::StringPiece path) override;
   std::unique_ptr<IFileCollectionIterator> Iterator() override;
   char GetDirSeparator() override;
 
@@ -74,7 +73,7 @@
 
   friend class FileCollectionIterator;
 
-  std::map<std::string, std::unique_ptr<IFile>> files_;
+  std::map<std::string, std::unique_ptr<IFile>, std::less<>> files_;
 };
 
 }  // namespace io