gn: Support build directories outside the source tree.

tools/gn/path_output_unittest.cc

Index: tools/gn/path_output_unittest.cc
diff --git a/tools/gn/path_output_unittest.cc b/tools/gn/path_output_unittest.cc
index 217f6dcfc3b30409dcd59bd289c0a25f98ce5d1c..131f55ec5faa2245caac72992709e121fbfbabbc 100644
--- a/tools/gn/path_output_unittest.cc
+++ b/tools/gn/path_output_unittest.cc
@@ -4,6 +4,7 @@
 
 #include <sstream>
 
+#include "base/files/file_path.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/output_file.h"
 #include "tools/gn/path_output.h"
@@ -12,7 +13,8 @@
 
 TEST(PathOutput, Basic) {
   SourceDir build_dir("//out/Debug/");
-  PathOutput writer(build_dir, ESCAPE_NONE);
+  base::StringPiece source_root("/source/root");
+  PathOutput writer(build_dir, source_root, ESCAPE_NONE);
   {
     // Normal source-root path.
     std::ostringstream out;
@@ -53,7 +55,8 @@ TEST(PathOutput, Basic) {
 // Same as basic but the output dir is the root.
 TEST(PathOutput, BasicInRoot) {
   SourceDir build_dir("//");
-  PathOutput writer(build_dir, ESCAPE_NONE);
+  base::StringPiece source_root("/source/root");
+  PathOutput writer(build_dir, source_root, ESCAPE_NONE);
   {
     // Normal source-root path.
     std::ostringstream out;
@@ -70,7 +73,8 @@ TEST(PathOutput, BasicInRoot) {
 
 TEST(PathOutput, NinjaEscaping) {
   SourceDir build_dir("//out/Debug/");
-  PathOutput writer(build_dir, ESCAPE_NINJA);
+  base::StringPiece source_root("/source/root");
+  PathOutput writer(build_dir, source_root, ESCAPE_NINJA);
   {
     // Spaces and $ in filenames.
     std::ostringstream out;
@@ -87,7 +91,8 @@ TEST(PathOutput, NinjaEscaping) {
 
 TEST(PathOutput, NinjaForkEscaping) {
   SourceDir build_dir("//out/Debug/");
-  PathOutput writer(build_dir, ESCAPE_NINJA_COMMAND);
+  base::StringPiece source_root("/source/root");
+  PathOutput writer(build_dir, source_root, ESCAPE_NINJA_COMMAND);
 
   // Spaces in filenames should get quoted on Windows.
   writer.set_escape_platform(ESCAPE_PLATFORM_WIN);
@@ -140,7 +145,8 @@ TEST(PathOutput, NinjaForkEscaping) {
 
 TEST(PathOutput, InhibitQuoting) {
   SourceDir build_dir("//out/Debug/");
-  PathOutput writer(build_dir, ESCAPE_NINJA_COMMAND);
+  base::StringPiece source_root("/source/root");
+  PathOutput writer(build_dir, source_root, ESCAPE_NINJA_COMMAND);
   writer.set_inhibit_quoting(true);
 
   writer.set_escape_platform(ESCAPE_PLATFORM_WIN);
@@ -163,7 +169,8 @@ TEST(PathOutput, InhibitQuoting) {
 TEST(PathOutput, WriteDir) {
   {
     SourceDir build_dir("//out/Debug/");
-    PathOutput writer(build_dir, ESCAPE_NINJA);
+    base::StringPiece source_root("/source/root");
+    PathOutput writer(build_dir, source_root, ESCAPE_NINJA);
     {
       std::ostringstream out;
       writer.WriteDir(out, SourceDir("//foo/bar/"),
@@ -259,7 +266,8 @@ TEST(PathOutput, WriteDir) {
   }
   {
     // Empty build dir writer.
-    PathOutput root_writer(SourceDir("//"), ESCAPE_NINJA);
+    base::StringPiece source_root("/source/root");
+    PathOutput root_writer(SourceDir("//"), source_root, ESCAPE_NINJA);
     {
       std::ostringstream out;
       root_writer.WriteDir(out, SourceDir("//"),