Revert of clang plugin: Compute absolute paths on Windows as well.

tools/clang/plugins/ChromeClassTester.cpp

Index: tools/clang/plugins/ChromeClassTester.cpp
diff --git a/tools/clang/plugins/ChromeClassTester.cpp b/tools/clang/plugins/ChromeClassTester.cpp
index f4a879c83dccfa1dec8ee5f77cf9d30bce07917e..cd508068e111399c0319dbebc49e707bd94fcea4 100644
--- a/tools/clang/plugins/ChromeClassTester.cpp
+++ b/tools/clang/plugins/ChromeClassTester.cpp
@@ -15,9 +15,6 @@
 
 #ifdef LLVM_ON_UNIX
 #include <sys/param.h>
-#endif
-#if defined(LLVM_ON_WIN32)
-#include <windows.h>
 #endif
 
 using namespace clang;
@@ -122,42 +119,27 @@
 
 #if defined(LLVM_ON_UNIX)
   // Resolve the symlinktastic relative path and make it absolute.
+  char resolvedPath[MAXPATHLEN];
   if (options_.no_realpath) {
     // Same reason as windows below, but we don't need to do
     // the '\\' manipulation on linux.
     filename.insert(filename.begin(), '/');
   } else if (realpath(filename.c_str(), resolvedPath)) {
-    char resolvedPath[MAXPATHLEN];
     filename = resolvedPath;
   }
 #endif
 
 #if defined(LLVM_ON_WIN32)
-  // Make path absolute.
-  if (options_.no_realpath) {
-    // This turns e.g. "gen/dir/file.cc" to "/gen/dir/file.cc" which lets the
-    // "/gen/" banned_dir work.
-    filename.insert(filename.begin(), '/');
-  } else {
-    // The Windows dance: Convert to UTF-16, call GetFullPathNameW, convert back
-    DWORD size_needed =
-        MultiByteToWideChar(CP_UTF8, 0, filename.data(), -1, nullptr, 0);
-    std::wstring utf16(size_needed, L'\0');
-    MultiByteToWideChar(CP_UTF8, 0, filename.data(), -1,
-                        &utf16[0], size_needed);
-
-    size_needed = GetFullPathNameW(utf16.data(), 0, nullptr, nullptr);
-    std::wstring full_utf16(size_needed, L'\0');
-    GetFullPathNameW(utf16.data(), full_utf16.size(), &full_utf16[0], nullptr);
-
-    size_needed = WideCharToMultiByte(CP_UTF8, 0, full_utf16.data(), -1,
-                                      nullptr, 0, nullptr, nullptr);
-    filename.resize(size_needed);
-    WideCharToMultiByte(CP_UTF8, 0, full_utf16.data(), -1, &filename[0],
-                        size_needed, nullptr, nullptr);
-  }
-
   std::replace(filename.begin(), filename.end(), '\\', '/');
+
+  // On Posix, realpath() has made the path absolute.  On Windows, this isn't
+  // necessarily true, so prepend a '/' to the path to make sure the
+  // banned_directories_ loop below works correctly.
+  // This turns e.g. "gen/dir/file.cc" to "/gen/dir/file.cc" which lets the
+  // "/gen/" banned_dir work.
+  // This seems simpler than converting to utf16, calling GetFullPathNameW(),
+  // and converting back to utf8.
+  filename.insert(filename.begin(), '/');
 #endif
 
   for (const std::string& allowed_dir : allowed_directories_) {