Include objidl.h in fx_win32_gdipext.cpp.

Do IWYU, as the file fails to compile with some toolchains.

Change-Id: Ifef7318da623530c1d5a0ba6978610c5d1b983eb
Reviewed-on: https://pdfium-review.googlesource.com/c/47470
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/core/fxge/win32/fx_win32_gdipext.cpp b/core/fxge/win32/fx_win32_gdipext.cpp
index 8e80b50..ea3db4d 100644
--- a/core/fxge/win32/fx_win32_gdipext.cpp
+++ b/core/fxge/win32/fx_win32_gdipext.cpp
@@ -6,6 +6,8 @@
 
 #include <windows.h>
 
+#include <objidl.h>
+
 #include <algorithm>
 #include <memory>
 #include <sstream>