Omnibox - Send Blank Query on Warm-Up Suggest Server Request

Fixes code and corresponding text.

Tested change interactively using the repro steps on the bug.

Bug: 868486
Change-Id: Id81cbddf28242b6c4efe5c50595fdb393d59d5b1
Reviewed-on: https://chromium-review.googlesource.com/1154432
Commit-Queue: Mark Pearson <mpearson@chromium.org>
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579095}

chrome/browser/autocomplete/search_provider_unittest.cc

@@ -3672,11 +3672,12 @@ TEST_F(SearchProviderTest, SendsWarmUpRequestOnFocus) {
     base::RunLoop().RunUntilIdle();
     EXPECT_FALSE(provider_->done());
     EXPECT_TRUE(provider_->matches().empty());
-    // Make sure the default provider's suggest service was queried.
-    EXPECT_TRUE(test_url_loader_factory_.IsPending("http://defaultturl2/f"));
+    // Make sure the default provider's suggest service was queried with an
+    // empty query.
+    EXPECT_TRUE(test_url_loader_factory_.IsPending("http://defaultturl2/"));
     // Even if the fetcher returns results, we should still have no suggestions
     // (though the provider should now be done).
-    test_url_loader_factory_.AddResponse("http://defaultturl2/f",
+    test_url_loader_factory_.AddResponse("http://defaultturl2/",
                                          R"(["",["a", "b"],[],[],{}])");
     RunTillProviderDone();
     EXPECT_TRUE(provider_->done());

components/omnibox/browser/search_provider.cc

@@ -892,8 +892,14 @@ std::unique_ptr<network::SimpleURLLoader> SearchProvider::CreateSuggestLoader(
     search_term_args.prefetch_query_type =
         base::UTF16ToUTF8(prefetch_data_.query_type);
   }
+
+  // If the request is from omnibox focus, send empty search term args. The
+  // purpose of such a request is to signal the server to warm up; no info
+  // is required.
   GURL suggest_url(template_url->suggestions_url_ref().ReplaceSearchTerms(
-      search_term_args,
+      input.from_omnibox_focus()
+          ? TemplateURLRef::SearchTermsArgs(base::string16())
+          : search_term_args,
       client()->GetTemplateURLService()->search_terms_data()));
   if (!suggest_url.is_valid())
     return nullptr;