Revert change of DCHECK to CHECK for bug validation

This DCHECK was added to validate the hypothesized cause of a bug. The
change is no longer necessary and shouldn't be included in the release.

Bug: 959194
Bug: 1004429
Change-Id: I48ddf24dfef0372f57d3705600918fe43e6744df
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1803670Reviewed-by: Josh Karlin <jkarlin@chromium.org>
Commit-Queue: Alex Turner <alexmt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697208}

net/http/http_cache_transaction.cc

@@ -1428,7 +1428,7 @@ int HttpCache::Transaction::DoDoneHeadersAddToEntryComplete(int result) {
   // created a new ActiveEntry (new_entry_) to write to (and doomed the old
   // one). Now that the new entry has been created, start writing the response.
 
-  CHECK_EQ(result, OK);
+  DCHECK_EQ(result, OK);
   DCHECK_EQ(mode_, WRITE);
   DCHECK(new_entry_);
   DCHECK(response_.headers);