Remove ContentSuggestion::salient_image_url_.

Review-Url: https://codereview.chromium.org/2297903004
Cr-Commit-Position: refs/heads/master@{#415610}

components/ntp_snippets/content_suggestion.h

@@ -77,7 +77,6 @@ class ContentSuggestion {
   GURL amp_url_;
   base::string16 title_;
   base::string16 snippet_text_;
-  GURL salient_image_url_;
   base::Time publish_date_;
   base::string16 publisher_name_;
   float score_;

components/ntp_snippets/ntp_snippets_service_unittest.cc

@@ -455,7 +455,6 @@ TEST_F(NTPSnippetsServiceTest, Full) {
   EXPECT_EQ(MakeUniqueID(*service, kSnippetUrl), suggestion.id());
   EXPECT_EQ(kSnippetTitle, base::UTF16ToUTF8(suggestion.title()));
   EXPECT_EQ(kSnippetText, base::UTF16ToUTF8(suggestion.snippet_text()));
-  // EXPECT_EQ(GURL(kSnippetSalientImage), suggestion.salient_image_url());
   EXPECT_EQ(GetDefaultCreationTime(), suggestion.publish_date());
   EXPECT_EQ(kSnippetPublisherName,
             base::UTF16ToUTF8(suggestion.publisher_name()));