Make an error message verbose to investigate a un-reproducible bug....

chrome/common/extensions/extension_unpacker.cc

Index: chrome/common/extensions/extension_unpacker.cc
===================================================================
--- chrome/common/extensions/extension_unpacker.cc	(revision 43601)
+++ chrome/common/extensions/extension_unpacker.cc	(working copy)
@@ -41,7 +41,7 @@
 
 // Errors
 const char* kCouldNotCreateDirectoryError =
-    "Could not create directory for unzipping.";
+    "Could not create directory for unzipping: ";
 const char* kCouldNotDecodeImageError = "Could not decode theme image.";
 const char* kCouldNotUnzipExtension = "Could not unzip extension.";
 const char* kPathNamesMustBeAbsoluteOrLocalError =
@@ -150,7 +150,12 @@
   temp_install_dir_ =
       extension_path_.DirName().AppendASCII(kTempExtensionName);
   if (!file_util::CreateDirectory(temp_install_dir_)) {
-    SetError(kCouldNotCreateDirectoryError);
+#if defined(OS_WIN)
+    std::string dir_string = WideToUTF8(temp_install_dir_.value());
+#else
+    std::string dir_string = temp_install_dir_.value();
+#endif
+    SetError(kCouldNotCreateDirectoryError + dir_string);
     return false;
   }