Do IWYU to fix building with gcc.

This is likely due to https://pdfium-review.googlesource.com/69071
reducing the numbers of headers being included.

Change-Id: Ia838f2f5ebda7a75f96a1e2541c4f0ed801ec9ec
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/69136
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
diff --git a/core/fxge/dib/cfx_dibitmap.cpp b/core/fxge/dib/cfx_dibitmap.cpp
index c5ee2c5..047d8ae 100644
--- a/core/fxge/dib/cfx_dibitmap.cpp
+++ b/core/fxge/dib/cfx_dibitmap.cpp
@@ -6,6 +6,8 @@
 
 #include "core/fxge/dib/cfx_dibitmap.h"
 
+#include <limits.h>
+
 #include <limits>
 #include <memory>
 #include <utility>
diff --git a/fpdfsdk/fpdf_annot_unittest.cpp b/fpdfsdk/fpdf_annot_unittest.cpp
index fd4d702..7ddd579 100644
--- a/fpdfsdk/fpdf_annot_unittest.cpp
+++ b/fpdfsdk/fpdf_annot_unittest.cpp
@@ -4,6 +4,8 @@
 
 #include "public/fpdf_annot.h"
 
+#include <limits.h>
+
 #include <vector>
 
 #include "constants/annotation_common.h"
diff --git a/fpdfsdk/fpdf_attachment.cpp b/fpdfsdk/fpdf_attachment.cpp
index 529f3e6..7c47fb6 100644
--- a/fpdfsdk/fpdf_attachment.cpp
+++ b/fpdfsdk/fpdf_attachment.cpp
@@ -4,6 +4,8 @@
 
 #include "public/fpdf_attachment.h"
 
+#include <limits.h>
+
 #include <memory>
 #include <utility>
 
diff --git a/fpdfsdk/fpdf_flatten.cpp b/fpdfsdk/fpdf_flatten.cpp
index 1f949cb..45b6c35 100644
--- a/fpdfsdk/fpdf_flatten.cpp
+++ b/fpdfsdk/fpdf_flatten.cpp
@@ -6,6 +6,8 @@
 
 #include "public/fpdf_flatten.h"
 
+#include <limits.h>
+
 #include <algorithm>
 #include <memory>
 #include <utility>