Add begin()/end() to ByteArray.

This allows this type to meet the requirements of e.g.
std::ranges::range, which is necessary for it to work with the
std::span range constructor, or the "non-legacy" constructor for
Chromium's base::span.

Fixes a number of IWYU problems along the way, to silence checks.

Bug: chromium:364987728
PiperOrigin-RevId: 689841844

internal/platform/byte_array.h

@@ -17,19 +17,19 @@
 
 #include <algorithm>
 #include <array>
-#include <cstdint>
 #include <cstring>
 #include <string>
-#include <type_traits>
 #include <utility>
 
-#include "absl/strings/str_cat.h"
 #include "absl/strings/string_view.h"
 
 namespace nearby {
 
 class ByteArray {
  public:
+  using iterator = std::string::iterator;
+  using const_iterator = std::string::const_iterator;
+
   // Create an empty ByteArray
   ByteArray() = default;
   template <size_t N>
@@ -84,6 +84,16 @@ class ByteArray {
   size_t size() const { return data_.size(); }
   bool Empty() const { return data_.empty(); }
 
+  // Iterators. These allow `ByteArray` to meet the requirements of
+  // `std::ranges::contiguous_range`, which in turn make it implicitly
+  // convertible to e.g. `std::span`.
+  iterator begin() { return data_.begin(); }
+  const_iterator begin() const { return data_.begin(); }
+  const_iterator cbegin() const { return data_.cbegin(); }
+  iterator end() { return data_.end(); }
+  const_iterator end() const { return data_.end(); }
+  const_iterator cend() const { return data_.cend(); }
+
   friend bool operator==(const ByteArray& lhs, const ByteArray& rhs);
   friend bool operator!=(const ByteArray& lhs, const ByteArray& rhs);
   friend bool operator<(const ByteArray& lhs, const ByteArray& rhs);