Make rebase_path() aware of Windows drive letter capitalization

tools/gn/filesystem_utils_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 "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/platform_thread.h"
@@ skipping 470 matching lines @@
   EXPECT_EQ("../../path/to/foo",
             RebasePath("/path/to/foo", SourceDir("/source/root"),
                        base::StringPiece("/x/y/z")));
   EXPECT_EQ("../../../path/to/foo",
             RebasePath("/path/to/foo", SourceDir("/source/root/a"),
                        base::StringPiece("/x/y/z")));
   EXPECT_EQ("../../../../path/to/foo",
             RebasePath("/path/to/foo", SourceDir("/source/root/a/b"),
                        base::StringPiece("/x/y/z")));
 
+#if defined(OS_WIN)
+  // Test corrections while rebasing Windows-style absolute paths.
+  EXPECT_EQ("../../../../path/to/foo",
+            RebasePath("C:/path/to/foo", SourceDir("//a/b"),
+                       base::StringPiece("/C:/source/root")));
+  EXPECT_EQ("../../../../path/to/foo",
+            RebasePath("/C:/path/to/foo", SourceDir("//a/b"),
+                       base::StringPiece("C:/source/root")));
+  EXPECT_EQ("../../../../path/to/foo",
+            RebasePath("/C:/path/to/foo", SourceDir("//a/b"),
+                       base::StringPiece("/c:/source/root")));
+  EXPECT_EQ("../../../../path/to/foo",
+            RebasePath("/c:/path/to/foo", SourceDir("//a/b"),
+                       base::StringPiece("c:/source/root")));
+  EXPECT_EQ("../../../../path/to/foo",
+            RebasePath("/c:/path/to/foo", SourceDir("//a/b"),
+                       base::StringPiece("C:/source/root")));
+#endif
 }
 
 TEST(FilesystemUtils, DirectoryWithNoLastSlash) {
   EXPECT_EQ("", DirectoryWithNoLastSlash(SourceDir()));
   EXPECT_EQ("/.", DirectoryWithNoLastSlash(SourceDir("/")));
   EXPECT_EQ("//.", DirectoryWithNoLastSlash(SourceDir("//")));
   EXPECT_EQ("//foo", DirectoryWithNoLastSlash(SourceDir("//foo/")));
   EXPECT_EQ("/bar", DirectoryWithNoLastSlash(SourceDir("/bar/")));
 }
 
@@ skipping 277 matching lines @@
   EXPECT_EQ("gen/", GetToolchainGenDirAsOutputFile(&settings).value());
   EXPECT_EQ("//obj/",
             GetOutputDirForSourceDir(&settings, SourceDir("//")).value());
   EXPECT_EQ("obj/",
             GetOutputDirForSourceDirAsOutputFile(
                 &settings, SourceDir("//")).value());
   EXPECT_EQ("gen/",
             GetGenDirForSourceDirAsOutputFile(
                 &settings, SourceDir("//")).value());
 }