gn win: Fix potentially uninitialized variable warning in zip_internal

third_party/zlib/google/zip_internal.cc

Index: third_party/zlib/google/zip_internal.cc
diff --git a/third_party/zlib/google/zip_internal.cc b/third_party/zlib/google/zip_internal.cc
index 6349b7a5e8c6b35d5dfab6ade16e00d6f9d994cc..5ed202432fe6ffd48b4d52b19e9eb0220e16081b 100644
--- a/third_party/zlib/google/zip_internal.cc
+++ b/third_party/zlib/google/zip_internal.cc
@@ -37,13 +37,11 @@ typedef struct {
 // Its only difference is that it treats the char* as UTF8 and
 // uses the Unicode version of CreateFile.
 void* ZipOpenFunc(void *opaque, const char* filename, int mode) {
-  DWORD desired_access, creation_disposition;
-  DWORD share_mode, flags_and_attributes;
+  DWORD desired_access = 0, creation_disposition = 0;
+  DWORD share_mode = 0, flags_and_attributes = 0;
   HANDLE file = 0;
   void* ret = NULL;
 
-  desired_access = share_mode = flags_and_attributes = 0;
-
   if ((mode & ZLIB_FILEFUNC_MODE_READWRITEFILTER) == ZLIB_FILEFUNC_MODE_READ) {
     desired_access = GENERIC_READ;
     creation_disposition = OPEN_EXISTING;