Clear the received slices in DownloadItemImpl when etag changed.

content/browser/download/download_item_impl.cc

Index: content/browser/download/download_item_impl.cc
diff --git a/content/browser/download/download_item_impl.cc b/content/browser/download/download_item_impl.cc
index 5c2286bb11e6e38aafc0ea569ea1ea3040947b3a..991d31c8dcc0767f3da740f65a5b2b70644b2645 100644
--- a/content/browser/download/download_item_impl.cc
+++ b/content/browser/download/download_item_impl.cc
@@ -1028,8 +1028,11 @@ void DownloadItemImpl::UpdateValidatorsOnResumption(
   if (chain_iter != new_create_info.url_chain.end())
     origin_state |= ORIGIN_STATE_ON_RESUMPTION_ADDITIONAL_REDIRECTS;
   if (etag_ != new_create_info.etag ||
-      last_modified_time_ != new_create_info.last_modified)
+      last_modified_time_ != new_create_info.last_modified) {
+    received_slices_.clear();
+    received_bytes_ = 0;

[qinmin, 2017/04/07 23:37:43]

you either need to do this after RecordOriginStateOnResumption(), or you have to
add a new boolean here, otherwise RecordOriginStateOnResumption() will record
the wrong metric.

So either:
bool is_partial = (received_bytes_ != 0);
if (etag_!=.....) {
  received_slices_.clear();
  received_bytes_ = 0;
}
RecordOriginStateOnResumption(is_partial, origin_state);


Or: 
if (etag_!=.....) {
  received_slices_.clear();
}
RecordOriginStateOnResumption(received_bytes_ != 0, origin_state);
if (etag_!=.....) {
  received_bytes_ = 0;
}

[xingliu, 2017/04/08 02:29:13]

Oh, I see, thanks for the suggestion, didn't notice it uses the received_bytes_
here.

     origin_state |= ORIGIN_STATE_ON_RESUMPTION_VALIDATORS_CHANGED;
+  }
   if (content_disposition_ != new_create_info.content_disposition)
     origin_state |= ORIGIN_STATE_ON_RESUMPTION_CONTENT_DISPOSITION_CHANGED;
   RecordOriginStateOnResumption(received_bytes_ != 0, origin_state);
@@ -1289,7 +1292,8 @@ void DownloadItemImpl::StartDownload() {
                  // Safe because we control download file lifetime.
                  base::Unretained(download_file_.get()),
                  base::Bind(&DownloadItemImpl::OnDownloadFileInitialized,
-                            weak_ptr_factory_.GetWeakPtr())));
+                            weak_ptr_factory_.GetWeakPtr()),
+                 received_slices_));
 }
 
 void DownloadItemImpl::OnDownloadFileInitialized(