Absolute path fixes for gn.

tools/gn/label.cc

Index: tools/gn/label.cc
diff --git a/tools/gn/label.cc b/tools/gn/label.cc
index 095128d81e2014856e9bee4d4e45ebd509f0c162..ca294c8c9cddf5f37140fd0a5eacac921e512954 100644
--- a/tools/gn/label.cc
+++ b/tools/gn/label.cc
@@ -6,6 +6,7 @@
 
 #include "base/logging.h"
 #include "tools/gn/err.h"
+#include "tools/gn/filesystem_utils.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/value.h"
 
@@ -93,8 +94,14 @@ bool Resolve(const SourceDir& current_dir,
              Err* err) {
   // To workaround the problem that StringPiece operator[] doesn't return a ref.
   const char* input_str = input.data();
-
-  size_t path_separator = input.find_first_of(":(");
+  size_t offset = 0;
+#if defined(OS_WIN)

[brettw, 2015/01/20 21:05:00]

On Windows, this accepts either "/C:/foo" or "C:/foo" I think. I'm not sure this
condition is correct. I think we should probably prohibit absolute paths that
don't begin in slashes here (the current behavior is to support paths returned
by third party tools, and these normally won't return label names). Can we also
add unit tests for these cases?

+  if (IsPathAbsolute(input)) {
+    // Skip over the drive letter colon.
+    offset = 3;
+  }
+#endif
+  size_t path_separator = input.find_first_of(":(", offset);
   base::StringPiece location_piece;
   base::StringPiece name_piece;
   base::StringPiece toolchain_piece;