Add total_length() and NumSlices() methods to QuicMemSliceSpan so that length...

Add total_length() and NumSlices() methods to QuicMemSliceSpan so that length of HTTP/3 data frame can be computed in QuicSpdyStream::WriteBodySlices().

no behavior change.

Merge internal change: 222285071

Change-Id: Ie3e2a120fc072a9d8329e33fe5cef778aa454c39
Reviewed-on: https://chromium-review.googlesource.com/c/1351584Reviewed-by: Ryan Hamilton <rch@chromium.org>
Commit-Queue: Renjie Tang <renjietang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612432}

net/third_party/quic/platform/api/quic_mem_slice_span.h

@@ -38,6 +38,12 @@ class QUIC_EXPORT_PRIVATE QuicMemSliceSpan {
   // Return data of the span at |index| by the form of a QuicStringPiece.
   QuicStringPiece GetData(int index) { return impl_.GetData(index); }
 
+  // Return the total length of the data inside the span.
+  QuicByteCount total_length() { return impl_.total_length(); }
+
+  // Return total number of slices in the span.
+  size_t NumSlices() { return impl_.NumSlices(); }
+
   bool empty() const { return impl_.empty(); }
 
  private:

net/third_party/quic/platform/impl/quic_mem_slice_span_impl.cc

@@ -41,4 +41,12 @@ QuicByteCount QuicMemSliceSpanImpl::SaveMemSlicesInSendBuffer(
   return saved_length;
 }
 
+QuicByteCount QuicMemSliceSpanImpl::total_length() {
+  QuicByteCount length = 0;
+  for (size_t i = 0; i < num_buffers_; ++i) {
+    length += lengths_[i];
+  }
+  return length;
+}
+
 }  // namespace quic

net/third_party/quic/platform/impl/quic_mem_slice_span_impl.h

@@ -36,6 +36,10 @@ class QUIC_EXPORT_PRIVATE QuicMemSliceSpanImpl {
     return QuicStringPiece(buffers_[index]->data(), lengths_[index]);
   }
 
+  QuicByteCount total_length();
+
+  size_t NumSlices() { return num_buffers_; }
+
   bool empty() const { return num_buffers_ == 0; }
 
  private: