Add GN function get_label_info

tools/gn/scope_per_file_provider_unittest.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/build_settings.h"
 #include "tools/gn/scope_per_file_provider.h"
 #include "tools/gn/settings.h"
 #include "tools/gn/test_with_scope.h"
 #include "tools/gn/toolchain.h"
@@ skipping 17 matching lines @@
     //EXPECT_EQ("//toolchain:default",    GPV(variables::kDefaultToolchain));
     EXPECT_EQ("//out/Debug",            GPV(variables::kRootBuildDir));
     EXPECT_EQ("//out/Debug/gen",        GPV(variables::kRootGenDir));
     EXPECT_EQ("//out/Debug",            GPV(variables::kRootOutDir));
     EXPECT_EQ("//out/Debug/gen/source", GPV(variables::kTargetGenDir));
     EXPECT_EQ("//out/Debug/obj/source", GPV(variables::kTargetOutDir));
   }
 
   // Test some with an alternate toolchain.
   {
-    Settings settings(test.build_settings(), "tc");
+    Settings settings(test.build_settings(), "tc/");
     Toolchain toolchain(&settings, Label(SourceDir("//toolchain/"), "tc"));
     settings.set_toolchain_label(toolchain.label());
 
     Scope scope(&settings);
     scope.set_source_dir(SourceDir("//source/"));
     ScopePerFileProvider provider(&scope, true);
 
     EXPECT_EQ("//toolchain:tc",            GPV(variables::kCurrentToolchain));
     // See above.
     //EXPECT_EQ("//toolchain:default",       GPV(variables::kDefaultToolchain));
     EXPECT_EQ("//out/Debug",               GPV(variables::kRootBuildDir));
     EXPECT_EQ("//out/Debug/tc/gen",        GPV(variables::kRootGenDir));
     EXPECT_EQ("//out/Debug/tc",            GPV(variables::kRootOutDir));
     EXPECT_EQ("//out/Debug/tc/gen/source", GPV(variables::kTargetGenDir));
     EXPECT_EQ("//out/Debug/tc/obj/source", GPV(variables::kTargetOutDir));
   }
 }