Absolute path fixes for gn.

tools/gn/label_pattern.cc

 // Copyright 2014 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/label_pattern.h"
 
+#include "base/strings/string_util.h"
 #include "tools/gn/err.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/value.h"
 
 const char kLabelPattern_Help[] =
     "Label patterns\n"
     "\n"
     "  A label pattern is a way of expressing one or more labels in a portion\n"
     "  of the source tree. They are not general regular expressions.\n"
     "\n"
@@ skipping 97 matching lines @@
     if (err->has_error())
       return LabelPattern();
 
     // Trim off the toolchain for the processing below.
     str = str.substr(0, open_paren);
   }
 
   // Extract path and name.
   base::StringPiece path;
   base::StringPiece name;
-  size_t colon = str.find(':');
+  size_t offset = 0;
+#if defined(OS_WIN)
+  if (IsPathAbsolute(str)) {
+    if (str[0] != '/') {
+      *err = Err(value, "Bad absolute path.",
+                 "Absolute paths must be of the form /C:\\ but this is \"" +
+                     str.as_string() + "\".");
+      return LabelPattern();
+    }
+    if (str.size() > 3 && str[2] == ':' && IsSlash(str[3]) &&
+        IsAsciiAlpha(str[1])) {
+      // Skip over the drive letter colon.
+      offset = 3;
+    }
+  }
+#endif
+  size_t colon = str.find(':', offset);
   if (colon == std::string::npos) {
     path = base::StringPiece(str);
   } else {
     path = str.substr(0, colon);
     name = str.substr(colon + 1);
   }
 
   // The path can have these forms:
   //   1. <empty>  (use current dir)
   //   2. <non wildcard stuff>  (send through directory resolution)
@@ skipping 103 matching lines @@
       break;
   }
 
   if (!toolchain_.is_null()) {
     result.push_back('(');
     result.append(toolchain_.GetUserVisibleName(false));
     result.push_back(')');
   }
   return result;
 }