Adds a Fetch() method to the ContentSuggestionService which asks any provider to provide more conte…

components/ntp_snippets/physical_web_pages/physical_web_page_suggestions_provider.cc

Index: components/ntp_snippets/physical_web_pages/physical_web_page_suggestions_provider.cc
diff --git a/components/ntp_snippets/physical_web_pages/physical_web_page_suggestions_provider.cc b/components/ntp_snippets/physical_web_pages/physical_web_page_suggestions_provider.cc
index f1f30982be07637a35f3f0591c9538c9f48bf29f..6cfd343d53a0450c3af2e32f5c417115da9fa031 100644
--- a/components/ntp_snippets/physical_web_pages/physical_web_page_suggestions_provider.cc
+++ b/components/ntp_snippets/physical_web_pages/physical_web_page_suggestions_provider.cc
@@ -4,6 +4,8 @@
 
 #include "components/ntp_snippets/physical_web_pages/physical_web_page_suggestions_provider.h"
 
+#include <utility>
+
 #include "base/bind.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
@@ -91,6 +93,16 @@ void PhysicalWebPageSuggestionsProvider::FetchSuggestionImage(
       FROM_HERE, base::Bind(callback, gfx::Image()));
 }
 
+void PhysicalWebPageSuggestionsProvider::Fetch(
+    const Category& category,
+    const std::set<std::string>& known_suggestion_ids,
+    FetchingCallback callback) {
+  NOTREACHED();
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE,
+      base::Bind(callback, base::Passed(std::vector<ContentSuggestion>())));
+}
+
 void PhysicalWebPageSuggestionsProvider::ClearHistory(
     base::Time begin,
     base::Time end,