Navigation Predictor: Simplify the browser tests

Simplify the browser tests by not checking for when the
experiment is disabled.

Also, add DCHECKs to the cc file to ensure that the
navigation predictor mojo binding object is
created only if the field trial is enabled.

Change-Id: I24189c75994e73a1f30d1a7aecc6d7bdaf4e8857
Bug: 903945
TBR: ryansturm@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/1349873Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610915}

chrome/browser/navigation_predictor/navigation_predictor.cc

@@ -105,6 +105,11 @@ NavigationPredictor::~NavigationPredictor() {
 void NavigationPredictor::Create(
     blink::mojom::AnchorElementMetricsHostRequest request,
     content::RenderFrameHost* render_frame_host) {
+  DCHECK(base::FeatureList::IsEnabled(
+      blink::features::kRecordAnchorMetricsClicked));
+  DCHECK(base::FeatureList::IsEnabled(
+      blink::features::kRecordAnchorMetricsVisible));
+
   // Only valid for the main frame.
   if (render_frame_host->GetParent())
     return;
@@ -195,6 +200,8 @@ TemplateURLService* NavigationPredictor::GetTemplateURLService() const {
 void NavigationPredictor::ReportAnchorElementMetricsOnClick(
     blink::mojom::AnchorElementMetricsPtr metrics) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  DCHECK(base::FeatureList::IsEnabled(
+      blink::features::kRecordAnchorMetricsClicked));
 
   if (browser_context_->IsOffTheRecord())
     return;
@@ -396,6 +403,9 @@ void NavigationPredictor::MergeMetricsSameTargetUrl(
 void NavigationPredictor::ReportAnchorElementMetricsOnLoad(
     std::vector<blink::mojom::AnchorElementMetricsPtr> metrics) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  DCHECK(base::FeatureList::IsEnabled(
+      blink::features::kRecordAnchorMetricsVisible));
+
   // Each document should only report metrics once when page is loaded.
   DCHECK(navigation_scores_map_.empty());
 

chrome/browser/navigation_predictor/navigation_predictor_unittest.cc

@@ -8,10 +8,12 @@
 
 #include "base/run_loop.h"
 #include "base/test/metrics/histogram_tester.h"
+#include "base/test/scoped_feature_list.h"
 #include "chrome/test/base/chrome_render_view_host_test_harness.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/blink/public/common/features.h"
 #include "third_party/blink/public/mojom/loader/navigation_predictor.mojom.h"
 #include "url/gurl.h"
 
@@ -24,6 +26,10 @@ class TestNavigationPredictor : public NavigationPredictor {
       content::RenderFrameHost* render_frame_host)
       : NavigationPredictor(render_frame_host), binding_(this) {
     binding_.Bind(std::move(request));
+    const std::vector<base::Feature> features = {
+        blink::features::kRecordAnchorMetricsVisible,
+        blink::features::kRecordAnchorMetricsClicked};
+    feature_list_.InitWithFeatures(features, {});
   }
 
   ~TestNavigationPredictor() override {}
@@ -46,6 +52,8 @@ class TestNavigationPredictor : public NavigationPredictor {
   // Maps from target URL to area rank of the anchor element.
   mutable std::map<GURL, int> area_rank_map_;
 
+  base::test::ScopedFeatureList feature_list_;
+
   // Used to bind Mojo interface
   mojo::Binding<AnchorElementMetricsHost> binding_;
 };