gn: Support build directories outside the source tree.

tools/gn/visibility_unittest.cc

Index: tools/gn/visibility_unittest.cc
diff --git a/tools/gn/visibility_unittest.cc b/tools/gn/visibility_unittest.cc
index 8be2db67facbcc6683806c5f730904e7bf4430a8..0da325b771b29565a250e9acc0b43a7a98728eec 100644
--- a/tools/gn/visibility_unittest.cc
+++ b/tools/gn/visibility_unittest.cc
@@ -16,7 +16,8 @@ TEST(Visibility, CanSeeMe) {
 
   Err err;
   Visibility vis;
-  ASSERT_TRUE(vis.Set(SourceDir("//"), list, &err));
+  base::FilePath source_root("/source/root");
+  ASSERT_TRUE(vis.Set(source_root, SourceDir("//"), list, &err));
 
   EXPECT_FALSE(vis.CanSeeMe(Label(SourceDir("//random/"), "thing")));
   EXPECT_FALSE(vis.CanSeeMe(Label(SourceDir("//my/"), "notname")));
@@ -33,10 +34,11 @@ TEST(Visibility, CanSeeMe) {
 TEST(Visibility, Public) {
   Err err;
   Visibility vis;
+  base::FilePath source_root("/source/root");
 
   Value list(NULL, Value::LIST);
   list.list_value().push_back(Value(NULL, "*"));
-  ASSERT_TRUE(vis.Set(SourceDir("//"), list, &err));
+  ASSERT_TRUE(vis.Set(source_root, SourceDir("//"), list, &err));
 
   EXPECT_TRUE(vis.CanSeeMe(Label(SourceDir("//random/"), "thing")));
   EXPECT_TRUE(vis.CanSeeMe(Label(SourceDir("//"), "")));
@@ -45,7 +47,9 @@ TEST(Visibility, Public) {
 TEST(Visibility, Private) {
   Err err;
   Visibility vis;
-  ASSERT_TRUE(vis.Set(SourceDir("//"), Value(NULL, Value::LIST), &err));
+  base::FilePath source_root("/source/root");
+  ASSERT_TRUE(vis.Set(source_root, SourceDir("//"), Value(NULL, Value::LIST),
+                      &err));
 
   EXPECT_FALSE(vis.CanSeeMe(Label(SourceDir("//random/"), "thing")));
   EXPECT_FALSE(vis.CanSeeMe(Label(SourceDir("//"), "")));