pw_stream: fix ConserativeReadLimit for IntervalReader

Change-Id: Ifae2dc7678a0519843ca49a8d4ef587b1e49e62c
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/62141
Reviewed-by: David Rogers <davidrogers@google.com>
Commit-Queue: Ewout van Bekkum <ewout@google.com>
Pigweed-Auto-Submit: Ewout van Bekkum <ewout@google.com>
diff --git a/pw_stream/public/pw_stream/interval_reader.h b/pw_stream/public/pw_stream/interval_reader.h
index 43b020a..c412ed6 100644
--- a/pw_stream/public/pw_stream/interval_reader.h
+++ b/pw_stream/public/pw_stream/interval_reader.h
@@ -83,6 +83,12 @@
   Status DoSeek(ssize_t offset, Whence origin) final;
   size_t DoTell() const final { return current_ - start_; }
   void Check();
+  size_t ConservativeLimit(LimitType limit) const override {
+    if (limit == LimitType::kRead) {
+      return end_ - current_;
+    }
+    return 0;
+  }
 
   SeekableReader* source_reader_ = nullptr;
   size_t start_ = 0;