Implement pretty for several more types

Change-Id: I47ca96f5d8183de90cbd26e1386001536a6a6964
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/26201
Reviewed-by: Takuto Ikuta <tikuta@google.com>
Commit-Queue: Matt Stark <msta@google.com>

src/gn/output_file.cc

diff --git a/src/gn/output_file.cc b/src/gn/output_file.cc
index 6a159ea..745eb0b 100644
--- a/src/gn/output_file.cc
+++ b/src/gn/output_file.cc
@@ -36,3 +36,7 @@
   NormalizePath(&path);
   return SourceDir(std::move(path));
 }
+
+std::string Pretty(const OutputFile& file) {
+  return std::string(file.value());
+}

src/gn/output_file.h

diff --git a/src/gn/output_file.h b/src/gn/output_file.h
index 30d3a12..d3f19f2 100644
--- a/src/gn/output_file.h
+++ b/src/gn/output_file.h
@@ -7,6 +7,7 @@
 
 #include <stddef.h>
 
+#include <string>
 #include <string_view>
 
 #include "gn/string_atom.h"
@@ -41,6 +42,8 @@
   StringAtom value_;
 };
 
+std::string Pretty(const OutputFile& file);
+
 namespace std {
 
 template <>

src/gn/source_dir.cc

diff --git a/src/gn/source_dir.cc b/src/gn/source_dir.cc
index f34a637..87fa669 100644
--- a/src/gn/source_dir.cc
+++ b/src/gn/source_dir.cc
@@ -141,3 +141,7 @@
 base::FilePath SourceDir::Resolve(const base::FilePath& source_root) const {
   return ResolvePath(value_.str(), false, source_root);
 }
+
+std::string Pretty(const SourceDir& dir) {
+  return dir.value();
+}

src/gn/source_dir.h

diff --git a/src/gn/source_dir.h b/src/gn/source_dir.h
index 2a694cf..b01ef02 100644
--- a/src/gn/source_dir.h
+++ b/src/gn/source_dir.h
@@ -135,6 +135,8 @@
   StringAtom value_;
 };
 
+std::string Pretty(const SourceDir& dir);
+
 namespace std {
 
 template <>

src/gn/source_file.cc

diff --git a/src/gn/source_file.cc b/src/gn/source_file.cc
index ecc2d1e..195f0fb 100644
--- a/src/gn/source_file.cc
+++ b/src/gn/source_file.cc
@@ -235,3 +235,7 @@
 
   return allowlist->find(range.begin().file()->name()) != allowlist->end();
 }
+
+std::string Pretty(const SourceFile& file) {
+  return file.value();
+}

src/gn/source_file.h

diff --git a/src/gn/source_file.h b/src/gn/source_file.h
index f63c5dc..c7a6c80 100644
--- a/src/gn/source_file.h
+++ b/src/gn/source_file.h
@@ -137,6 +137,8 @@
   StringAtom value_;
 };
 
+std::string Pretty(const SourceFile& file);
+
 namespace std {
 
 template <>