clang/win: Let remaining chromium_code targets build with -Wextra.

chrome/child/pdf_child_init.cc

Index: chrome/child/pdf_child_init.cc
diff --git a/chrome/child/pdf_child_init.cc b/chrome/child/pdf_child_init.cc
index fe9a1a4f29dc6a3cb90a6069260f3dc47af5a9e0..4c327534ac0bd20ae55e2f48b3d329e6a528cad7 100644
--- a/chrome/child/pdf_child_init.cc
+++ b/chrome/child/pdf_child_init.cc
@@ -43,7 +43,7 @@ DWORD WINAPI GetFontDataPatch(HDC hdc,
                               DWORD offset,
                               LPVOID buffer,
                               DWORD length) {
-  int rv = g_original_get_font_data(hdc, table, offset, buffer, length);
+  DWORD rv = g_original_get_font_data(hdc, table, offset, buffer, length);
   if (rv == GDI_ERROR && hdc) {
     HFONT font = static_cast<HFONT>(GetCurrentObject(hdc, OBJ_FONT));