Inform server of dismissed articles.

components/ntp_snippets/ntp_snippets_service.cc

Index: components/ntp_snippets/ntp_snippets_service.cc
diff --git a/components/ntp_snippets/ntp_snippets_service.cc b/components/ntp_snippets/ntp_snippets_service.cc
index 1c8a12acfa6e90752082ce69e8841384db8ef89b..2d96c0c2d3329b998c2a64ef36328933121db02b 100644
--- a/components/ntp_snippets/ntp_snippets_service.cc
+++ b/components/ntp_snippets/ntp_snippets_service.cc
@@ -265,8 +265,13 @@ void NTPSnippetsService::FetchSnippetsFromHosts(
   if (snippets_.empty())
     UpdateCategoryStatus(CategoryStatus::AVAILABLE_LOADING);
 
-  snippets_fetcher_->FetchSnippetsFromHosts(
-      hosts, application_language_code_, kMaxSnippetCount, interactive_request);
+  std::set<std::string> excluded_ids;
+  for (const auto& snippet : dismissed_snippets_) {
+    excluded_ids.insert(snippet->id());

[tschumann, 2016/08/24 16:56:19]

i'm wondering if we should limit those, to say no more than 200 or so. but we
don't have them in chronological order, right?

[sfiera, 2016/08/24 17:08:28]

We have timestamps of creation and expiration, but not the time when we received
them from the server.

In any case, I assume that the server will only honor exclusions up to, say, 50
or so IDs. If, at that point, we stop returning new snippets, it will serve as a
throttle on dismissing more snippets.

[tschumann, 2016/08/24 18:24:07]

Good point! This of course assumes that we don't screw up expiration dates some
day. Would be bad to send large requests just because the articles only expire
in 2033 for some reason ;-)
I might be a bit paranoid though...

[Marc Treib, 2016/08/25 09:01:41]

+1 for some hard limit, just to be safe. I'd put that limit into the fetcher
though, not here.

[sfiera, 2016/08/25 10:39:56]

Done (there, 100).

+  }
+  snippets_fetcher_->FetchSnippetsFromHosts(hosts, application_language_code_,
+                                            excluded_ids, kMaxSnippetCount,
+                                            interactive_request);
 }
 
 void NTPSnippetsService::RescheduleFetching() {