media: Add UMA stats for bytes going in and out of multibuffer cache

media/blink/resource_multibuffer_data_provider.cc

Index: media/blink/resource_multibuffer_data_provider.cc
diff --git a/media/blink/resource_multibuffer_data_provider.cc b/media/blink/resource_multibuffer_data_provider.cc
index 921aab925539f8402a236bda8539d6daa8962a1f..0bdde0aff18ce5a664dcd403499287b1f175821f 100644
--- a/media/blink/resource_multibuffer_data_provider.cc
+++ b/media/blink/resource_multibuffer_data_provider.cc
@@ -388,6 +388,8 @@ void ResourceMultiBufferDataProvider::DidReceiveData(const char* data,
   DCHECK(active_loader_);
   DCHECK_GT(data_length, 0);
 
+  url_data_->AddBytesReadFromNetwork(data_length);
+
   if (bytes_to_discard_) {
     uint64_t tmp = std::min<uint64_t>(bytes_to_discard_, data_length);
     data_length -= tmp;