gn: Support build directories outside the source tree.

tools/gn/source_dir_unittest.cc

Index: tools/gn/source_dir_unittest.cc
diff --git a/tools/gn/source_dir_unittest.cc b/tools/gn/source_dir_unittest.cc
index d2ea3aa7a1c4bd62b7d242f80a7ee7aaca7708ae..fb7562037f7ee00b6cdef041dbb580cfdfcb5833 100644
--- a/tools/gn/source_dir_unittest.cc
+++ b/tools/gn/source_dir_unittest.cc
@@ -8,48 +8,70 @@
 
 TEST(SourceDir, ResolveRelativeFile) {
   SourceDir base("//base/");
+  base::FilePath source_root("/source/root/");
 
   // Empty input is an error.
-  EXPECT_TRUE(base.ResolveRelativeFile("") == SourceFile());
+  EXPECT_TRUE(base.ResolveRelativeFile("", source_root) == SourceFile());
 
   // These things are directories, so should be an error.
-  EXPECT_TRUE(base.ResolveRelativeFile("//foo/bar/") == SourceFile());
-  EXPECT_TRUE(base.ResolveRelativeFile("bar/") == SourceFile());
+  EXPECT_TRUE(base.ResolveRelativeFile("//foo/bar/", source_root) ==
+              SourceFile());
+  EXPECT_TRUE(base.ResolveRelativeFile("bar/", source_root) ==
+              SourceFile());
 
   // Absolute paths should be passed unchanged.
-  EXPECT_TRUE(base.ResolveRelativeFile("//foo") == SourceFile("//foo"));
-  EXPECT_TRUE(base.ResolveRelativeFile("/foo") == SourceFile("/foo"));
+  EXPECT_TRUE(base.ResolveRelativeFile("//foo",source_root) ==
+              SourceFile("//foo"));
+  EXPECT_TRUE(base.ResolveRelativeFile("/foo", source_root) ==
+              SourceFile("/foo"));
 
   // Basic relative stuff.
-  EXPECT_TRUE(base.ResolveRelativeFile("foo") == SourceFile("//base/foo"));
-  EXPECT_TRUE(base.ResolveRelativeFile("./foo") == SourceFile("//base/foo"));
-  EXPECT_TRUE(base.ResolveRelativeFile("../foo") == SourceFile("//foo"));
-  EXPECT_TRUE(base.ResolveRelativeFile("../../foo") == SourceFile("//foo"));
+  EXPECT_TRUE(base.ResolveRelativeFile("foo", source_root) ==
+              SourceFile("//base/foo"));
+  EXPECT_TRUE(base.ResolveRelativeFile("./foo", source_root) ==
+              SourceFile("//base/foo"));
+  EXPECT_TRUE(base.ResolveRelativeFile("../foo", source_root) ==
+              SourceFile("//foo"));
+
+  // If the given relative path points outside the source root, we
+  // expect an absolute path.
+  EXPECT_TRUE(base.ResolveRelativeFile("../../foo", source_root) ==
+              SourceFile("/source/foo"));
 
 #if defined(OS_WIN)
   // Note that we don't canonicalize the backslashes to forward slashes.
   // This could potentially be changed in the future which would mean we should
   // just change the expected result.
-  EXPECT_TRUE(base.ResolveRelativeFile("C:\\foo\\bar.txt") ==
+  EXPECT_TRUE(base.ResolveRelativeFile("C:\\foo\\bar.txt", source_root) ==
               SourceFile("/C:/foo/bar.txt"));
 #endif
 }
 
 TEST(SourceDir, ResolveRelativeDir) {
   SourceDir base("//base/");
+  base::FilePath source_root("/source/root/");
 
   // Empty input is an error.
-  EXPECT_TRUE(base.ResolveRelativeDir("") == SourceDir());
+  EXPECT_TRUE(base.ResolveRelativeDir("", source_root) == SourceDir());
 
   // Absolute paths should be passed unchanged.
-  EXPECT_TRUE(base.ResolveRelativeDir("//foo") == SourceDir("//foo/"));
-  EXPECT_TRUE(base.ResolveRelativeDir("/foo") == SourceDir("/foo/"));
+  EXPECT_TRUE(base.ResolveRelativeDir("//foo", source_root) ==
+              SourceDir("//foo/"));
+  EXPECT_TRUE(base.ResolveRelativeDir("/foo", source_root) ==
+              SourceDir("/foo/"));
 
   // Basic relative stuff.
-  EXPECT_TRUE(base.ResolveRelativeDir("foo") == SourceDir("//base/foo/"));
-  EXPECT_TRUE(base.ResolveRelativeDir("./foo") == SourceDir("//base/foo/"));
-  EXPECT_TRUE(base.ResolveRelativeDir("../foo") == SourceDir("//foo/"));
-  EXPECT_TRUE(base.ResolveRelativeDir("../../foo/") == SourceDir("//foo/"));
+  EXPECT_TRUE(base.ResolveRelativeDir("foo", source_root) ==
+              SourceDir("//base/foo/"));
+  EXPECT_TRUE(base.ResolveRelativeDir("./foo", source_root) ==
+              SourceDir("//base/foo/"));
+  EXPECT_TRUE(base.ResolveRelativeDir("../foo", source_root) ==
+              SourceDir("//foo/"));
+
+  // If the given relative path points outside the source root, we
+  // expect an absolute path.
+  EXPECT_TRUE(base.ResolveRelativeDir("../../foo", source_root) ==
+              SourceDir("/source/foo/"));
 
 #if defined(OS_WIN)
   // Note that we don't canonicalize the existing backslashes to forward