Use std::extent to figure out the size of member arrays.

FX_ArraySize() is about to be removed in favor of pdfium::size().
However, pdfium::size() can't figure out the number of elements in a
member variable array in constexpr statements.

Change-Id: Ifea3b4fd8ed0ee9fe0e17872a39eff6e29cc71f2
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/69571
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

core/fpdfapi/font/cpdf_type3font.cpp

diff --git a/core/fpdfapi/font/cpdf_type3font.cpp b/core/fpdfapi/font/cpdf_type3font.cpp
index eae08ea..2cbf95c 100644
--- a/core/fpdfapi/font/cpdf_type3font.cpp
+++ b/core/fpdfapi/font/cpdf_type3font.cpp
@@ -7,6 +7,7 @@
 #include "core/fpdfapi/font/cpdf_type3font.h"
 
 #include <algorithm>
+#include <type_traits>
 #include <utility>
 
 #include "core/fpdfapi/font/cpdf_type3char.h"
@@ -74,7 +75,7 @@
     m_FontBBox = box.ToFxRect();
   }
 
-  static constexpr size_t kCharLimit = FX_ArraySize(m_CharWidthL);
+  static constexpr size_t kCharLimit = std::extent<decltype(m_CharWidthL)>();
   int StartChar = m_pFontDict->GetIntegerFor("FirstChar");
   if (StartChar >= 0 && static_cast<size_t>(StartChar) < kCharLimit) {
     const CPDF_Array* pWidthArray = m_pFontDict->GetArrayFor("Widths");

core/fpdfapi/page/cpdf_colorspace.cpp

diff --git a/core/fpdfapi/page/cpdf_colorspace.cpp b/core/fpdfapi/page/cpdf_colorspace.cpp
index ba22433..6b309cb 100644
--- a/core/fpdfapi/page/cpdf_colorspace.cpp
+++ b/core/fpdfapi/page/cpdf_colorspace.cpp
@@ -9,6 +9,7 @@
 #include <algorithm>
 #include <limits>
 #include <memory>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -842,8 +843,9 @@
   const CPDF_Array* pParam = pDict->GetArrayFor("Range");
   static constexpr float kDefaultRanges[kRangesCount] = {-100.0f, 100.0f,
                                                          -100.0f, 100.0f};
-  static_assert(FX_ArraySize(kDefaultRanges) == FX_ArraySize(m_Ranges),
-                "Range size mismatch");
+  static_assert(
+      FX_ArraySize(kDefaultRanges) == std::extent<decltype(m_Ranges)>(),
+      "Range size mismatch");
   for (size_t i = 0; i < FX_ArraySize(kDefaultRanges); ++i)
     m_Ranges[i] = pParam ? pParam->GetNumberAt(i) : kDefaultRanges[i];
   return 3;