[GN] Add support to rebase_path to resolve paths above the source root.

tools/gn/source_dir_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/err.h"
 #include "tools/gn/source_dir.h"
 #include "tools/gn/source_file.h"
 #include "tools/gn/value.h"
 
@@ skipping 43 matching lines @@
       Value(nullptr, "../foo"), &err, source_root) == SourceFile("//foo"));
   EXPECT_FALSE(err.has_error());
 
   // If the given relative path points outside the source root, we
   // expect an absolute path.
 #if defined(OS_WIN)
   EXPECT_TRUE(base.ResolveRelativeFile(
           Value(nullptr, "../../foo"), &err, source_root) ==
       SourceFile("/C:/source/foo"));
   EXPECT_FALSE(err.has_error());
+
+  EXPECT_TRUE(base.ResolveRelativeFile(
+          Value(nullptr, "//../foo"), &err, source_root) ==
+      SourceFile("/C:/source/foo"));
+  EXPECT_FALSE(err.has_error());
+
+  EXPECT_TRUE(base.ResolveRelativeFile(
+          Value(nullptr, "//../root/foo"), &err, source_root) ==
+      SourceFile("/C:/source/root/foo"));
+  EXPECT_FALSE(err.has_error());
+
+  EXPECT_TRUE(base.ResolveRelativeFile(
+          Value(nullptr, "//../../../foo/bar"), &err, source_root) ==
+      SourceFile("/foo/bar"));
+  EXPECT_FALSE(err.has_error());
 #else
   EXPECT_TRUE(base.ResolveRelativeFile(
           Value(nullptr, "../../foo"), &err, source_root) ==
       SourceFile("/source/foo"));
   EXPECT_FALSE(err.has_error());
+
+  EXPECT_TRUE(base.ResolveRelativeFile(
+          Value(nullptr, "//../foo"), &err, source_root) ==
+      SourceFile("/source/foo"));
+  EXPECT_FALSE(err.has_error());
+
+  EXPECT_TRUE(base.ResolveRelativeFile(
+          Value(nullptr, "//../root/foo"), &err, source_root) ==
+      SourceFile("/source/root/foo"));
+  EXPECT_FALSE(err.has_error());
+
+  EXPECT_TRUE(base.ResolveRelativeFile(
+          Value(nullptr, "//../../../foo/bar"), &err, source_root) ==
+      SourceFile("/foo/bar"));
+  EXPECT_FALSE(err.has_error());
 #endif
 
 #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(
           Value(nullptr, "C:\\foo\\bar.txt"), &err, source_root) ==
       SourceFile("/C:/foo/bar.txt"));
   EXPECT_FALSE(err.has_error());
@@ skipping 34 matching lines @@
       Value(nullptr, "../foo"), &err, source_root) == SourceDir("//foo/"));
   EXPECT_FALSE(err.has_error());
 
   // If the given relative path points outside the source root, we
   // expect an absolute path.
 #if defined(OS_WIN)
   EXPECT_TRUE(base.ResolveRelativeDir(
           Value(nullptr, "../../foo"), &err, source_root) ==
       SourceDir("/C:/source/foo/"));
   EXPECT_FALSE(err.has_error());
+  EXPECT_TRUE(base.ResolveRelativeDir(
+          Value(nullptr, "//../foo"), &err, source_root) ==
+      SourceDir("/C:/source/foo/"));
+  EXPECT_FALSE(err.has_error());
+  EXPECT_TRUE(base.ResolveRelativeDir(
+          Value(nullptr, "//.."), &err, source_root) ==
+      SourceDir("/C:/source/"));
+  EXPECT_FALSE(err.has_error());
 #else
   EXPECT_TRUE(base.ResolveRelativeDir(
           Value(nullptr, "../../foo"), &err, source_root) ==
       SourceDir("/source/foo/"));
   EXPECT_FALSE(err.has_error());
+  EXPECT_TRUE(base.ResolveRelativeDir(
+          Value(nullptr, "//../foo"), &err, source_root) ==
+      SourceDir("/source/foo/"));
+  EXPECT_FALSE(err.has_error());
+  EXPECT_TRUE(base.ResolveRelativeDir(
+          Value(nullptr, "//.."), &err, source_root) ==
+      SourceDir("/source/"));
+  EXPECT_FALSE(err.has_error());
 #endif
 
 #if defined(OS_WIN)
   // Canonicalize the existing backslashes to forward slashes and add a
   // leading slash if necessary.
   EXPECT_TRUE(base.ResolveRelativeDir(
       Value(nullptr, "\\C:\\foo"), &err) == SourceDir("/C:/foo/"));
   EXPECT_FALSE(err.has_error());
   EXPECT_TRUE(base.ResolveRelativeDir(
       Value(nullptr, "C:\\foo"), &err) == SourceDir("/C:/foo/"));
   EXPECT_FALSE(err.has_error());
 #endif
 }