Re-enable warning 4701 for GN build and some cleanup

Clean up three 4701 warnings (use potientially uninitialized variable)
which are the only ones left;
Re-enable warning 4701 for GN build;
Remove an unused data structure;

BUG=pdfium:29

Review URL: https://codereview.chromium.org/1885093002

1 files changed, 0 insertions, 1 deletions

diff --git a/BUILD.gn b/BUILD.gn
index 74903bf682..bb0b5cb3c6 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -44,7 +44,6 @@ config("pdfium_config") {
   if (is_win) {
     cflags += [
       "/wd4267",
-      "/wd4701",
     ]
   }