GCC: fix ambiguous reference to UnsafeInputHandlers

GCC sees multiple definitions. Add namespace to avoid confusion.

Bug: chromium:819294
Change-Id: Id8a5f87940c54a8dfb6b429448f5f454ccaa9e42
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/92490
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

fpdfsdk/cpdfsdk_baannot.h

diff --git a/fpdfsdk/cpdfsdk_baannot.h b/fpdfsdk/cpdfsdk_baannot.h
index 383ee8a..207c68b 100644
--- a/fpdfsdk/cpdfsdk_baannot.h
+++ b/fpdfsdk/cpdfsdk_baannot.h
@@ -28,7 +28,7 @@
 
   // CPDFSDK_Annot:
   CPDFSDK_BAAnnot* AsBAAnnot() override;
-  UnsafeInputHandlers* GetUnsafeInputHandlers() override;
+  CPDFSDK_Annot::UnsafeInputHandlers* GetUnsafeInputHandlers() override;
   CPDF_Annot::Subtype GetAnnotSubtype() const override;
   CFX_FloatRect GetRect() const override;
   CPDF_Annot* GetPDFAnnot() const override;

fpdfsdk/fpdfxfa/cpdfxfa_widget.h

diff --git a/fpdfsdk/fpdfxfa/cpdfxfa_widget.h b/fpdfsdk/fpdfxfa/cpdfxfa_widget.h
index 7346f8e..6fbce97 100644
--- a/fpdfsdk/fpdfxfa/cpdfxfa_widget.h
+++ b/fpdfsdk/fpdfxfa/cpdfxfa_widget.h
@@ -24,7 +24,7 @@
 
   // CPDFSDK_Annot:
   CPDFXFA_Widget* AsXFAWidget() override;
-  UnsafeInputHandlers* GetUnsafeInputHandlers() override;
+  CPDFSDK_Annot::UnsafeInputHandlers* GetUnsafeInputHandlers() override;
   CPDF_Annot::Subtype GetAnnotSubtype() const override;
   CFX_FloatRect GetRect() const override;
   void OnDraw(CFX_RenderDevice* pDevice,