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

tools/gn/source_dir.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 "tools/gn/source_dir.h"
 
 #include "base/logging.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/source_file.h"
 
@@ skipping 53 matching lines @@
     *err = Err(p, "File path ends in a slash.",
                "You specified the path\n  " + str + "\n"
                "and it ends in a slash, indicating you think it's a directory."
                "\nBut here you're supposed to be listing a file.");
     return ret;
   }
 
   if (str.size() >= 2 && str[0] == '/' && str[1] == '/') {
     // Source-relative.
     ret.value_.assign(str.data(), str.size());
-    NormalizePath(&ret.value_);
+    NormalizePath(&ret.value_, source_root);
     return ret;
   } else if (IsPathAbsolute(str)) {
     if (source_root.empty() ||
         !MakeAbsolutePathRelativeIfPossible(source_root, str, &ret.value_)) {
 #if defined(OS_WIN)
       // On Windows we'll accept "C:\foo" as an absolute path, which we want
       // to convert to "/C:..." here.
       if (str[0] != '/')
         ret.value_ = "/";
 #endif
@@ skipping 53 matching lines @@
                "You can't use empty strings as directories. "
                "That's just wrong.");
     return ret;
   }
 
   if (str.size() >= 2 && str[0] == '/' && str[1] == '/') {
     // Source-relative.
     ret.value_.assign(str.data(), str.size());
     if (!EndsWithSlash(ret.value_))
       ret.value_.push_back('/');
-    NormalizePath(&ret.value_);
+    NormalizePath(&ret.value_, source_root);
     return ret;
   } else if (IsPathAbsolute(str)) {
     if (source_root.empty() ||
         !MakeAbsolutePathRelativeIfPossible(source_root, str, &ret.value_)) {
 #if defined(OS_WIN)
       if (str[0] != '/')  // See the file case for why we do this check.
         ret.value_ = "/";
 #endif
       ret.value_.append(str.data(), str.size());
     }
@@ skipping 51 matching lines @@
   // String the double-leading slash for source-relative paths.
   converted.assign(&value_[2], value_.size() - 2);
   return source_root.Append(UTF8ToFilePath(converted))
       .NormalizePathSeparatorsTo('/');
 }
 
 void SourceDir::SwapValue(std::string* v) {
   value_.swap(*v);
   AssertValueSourceDirString(value_);
 }