Bug 1392609 Find returns an int32_t not a uint32_t r=froydnj

MozReview-Commit-ID: 8jBe7CGbAvM

--HG--
extra : rebase_source : f8f9963118658174e11364f2aed958dfe3a0cea7

xpcom/io/nsLocalFileWin.cpp

@@ -1205,7 +1205,7 @@ CleanupHandlerPath(nsString& aPath)
   aPath.Append(' ');
 
   // case insensitive
-  uint32_t index = aPath.Find(".exe ", true);
+  int32_t index = aPath.Find(".exe ", true);
   if (index == kNotFound)
     index = aPath.Find(".dll ", true);
   if (index == kNotFound)