Remove stray includes of cpdfsdk_helpers.h

And do IWYU where required.  Generally, this shouldn't be included
in other .h files as help is usually only required by the implementation.

Change-Id: Ic0f3ef58cbbcf33609c4cae0d313f8d8c53464c3
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/55931
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
diff --git a/fpdfsdk/cpdfsdk_annot.h b/fpdfsdk/cpdfsdk_annot.h
index 527e79e..2a4b713 100644
--- a/fpdfsdk/cpdfsdk_annot.h
+++ b/fpdfsdk/cpdfsdk_annot.h
@@ -13,7 +13,6 @@
 #include "core/fxcrt/observed_ptr.h"
 #include "core/fxcrt/unowned_ptr.h"
 #include "fpdfsdk/cfx_systemhandler.h"
-#include "fpdfsdk/cpdfsdk_helpers.h"
 
 class CFX_Matrix;
 class CFX_RenderDevice;
@@ -21,6 +20,8 @@
 class CPDF_RenderOptions;
 class CPDFSDK_BAAnnot;
 class CPDFSDK_PageView;
+class CPDFXFA_Page;
+class IPDF_Page;
 
 #ifdef PDF_ENABLE_XFA
 class CXFA_FFWidget;