[CSN] Record number of back navigations to a SRP

This CL adds a new metric that records the number back navigations to
a Google search result page in a search session. This is part of efforts
to record metrics for CSN stage 1.

See go/csn-design for more details on the project.

Change-Id: Ida5ac7358764a8c13da5aea8890957f77c6e2a47
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2616325Reviewed-by: Caitlin Fischer <caitlinfischer@google.com>
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Reviewed-by: Fred Mello <fredmello@chromium.org>
Reviewed-by: Mehran Mahmoudi <mahmoudi@chromium.org>
Commit-Queue: Yashar Dabiran <yashard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845675}

chrome/android/BUILD.gn

@@ -813,6 +813,7 @@ junit_binary("chrome_junit_tests") {
     "//chrome/browser/browser_controls/android:java",
     "//chrome/browser/browser_controls/android:junit",
     "//chrome/browser/contextmenu:java",
+    "//chrome/browser/continuous_search/internal:junit",
     "//chrome/browser/device:java",
     "//chrome/browser/device:junit",
     "//chrome/browser/download/android:java",

chrome/browser/continuous_search/DEPS

 include_rules = [
-  "+content/public/android/java/src/org/chromium/content_public/browser/LoadUrlParams.java",
+  "+content/public/android/java/src/org/chromium/content_public/browser",
 ]

chrome/browser/continuous_search/android/java/org/chromium/chrome/browser/continuous_search/ContinuousSearchTabHelper.java

@@ -19,10 +19,11 @@ public class ContinuousSearchTabHelper {
      * @param tab to enable continuous search support for.
      */
     public static void createForTab(Tab tab) {
-        if (!FeatureList.isNativeInitialized()
-                || !ChromeFeatureList.isEnabled(ChromeFeatureList.CONTINUOUS_SEARCH)) {
-            return;
-        }
+        if (!FeatureList.isNativeInitialized()) return;
+
+        if (!tab.isIncognito()) new BackNavigationTabObserver(tab);
+
+        if (!ChromeFeatureList.isEnabled(ChromeFeatureList.CONTINUOUS_SEARCH)) return;
 
         SearchResultUserData.createForTab(tab);
         SearchResultListCoordinator.createForTab(tab);

chrome/browser/continuous_search/internal/BUILD.gn

@@ -12,6 +12,7 @@ android_library("java") {
   annotation_processor_deps = [ "//base/android/jni_generator:jni_processor" ]
 
   sources = [
+    "android/java/src/org/chromium/chrome/browser/continuous_search/BackNavigationTabObserver.java",
     "android/java/src/org/chromium/chrome/browser/continuous_search/ContinuousSearchTabObserver.java",
     "android/java/src/org/chromium/chrome/browser/continuous_search/SearchResult.java",
     "android/java/src/org/chromium/chrome/browser/continuous_search/SearchResultGroup.java",
@@ -44,6 +45,27 @@ android_library("java") {
   resources_package = "org.chromium.chrome.browser.continuous_search"
 }
 
+android_library("junit") {
+  bypass_platform_checks = true
+  testonly = true
+
+  sources = [ "android/junit/org/chromium/chrome/browser/continuous_search/BackNavigationTabObserverTest.java" ]
+
+  deps = [
+    ":java",
+    "//base:base_java",
+    "//base:base_java_test_support",
+    "//base:base_junit_test_support",
+    "//chrome/browser/tab:java",
+    "//content/public/android:content_java",
+    "//third_party/android_deps:robolectric_all_java",
+    "//third_party/junit",
+    "//third_party/mockito:mockito_java",
+    "//url:gurl_java",
+    "//url:gurl_junit_test_support",
+  ]
+}
+
 android_resources("java_resources") {
   sources = [
     "android/java/res/layout/continuous_search_list_ad.xml",

chrome/browser/continuous_search/internal/android/java/src/org/chromium/chrome/browser/continuous_search/BackNavigationTabObserver.java

+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.continuous_search;
+
+import org.chromium.base.metrics.RecordHistogram;
+import org.chromium.chrome.browser.tab.EmptyTabObserver;
+import org.chromium.chrome.browser.tab.Tab;
+import org.chromium.chrome.browser.tab.TabHidingType;
+import org.chromium.content_public.browser.NavigationEntry;
+import org.chromium.content_public.browser.NavigationHistory;
+import org.chromium.url.GURL;
+
+/**
+ * A tab observer to record the number of back navigations to SRP
+ */
+public class BackNavigationTabObserver extends EmptyTabObserver {
+    private GURL mLastSrpUrl;
+    private GURL mLastVisitedUrl;
+    private int mBackNavigationCount;
+
+    public BackNavigationTabObserver(Tab tab) {
+        tab.addObserver(this);
+        mLastSrpUrl = null;
+        mLastVisitedUrl = null;
+        mBackNavigationCount = 0;
+    }
+
+    @Override
+    public void onPageLoadFinished(Tab tab, GURL url) {
+        // Ignore page reloads
+        if (url.equals(mLastVisitedUrl)) return;
+
+        if (tab.getWebContents() == null) return;
+        NavigationHistory history =
+                tab.getWebContents().getNavigationController().getNavigationHistory();
+        // Some tests don't mock Tab completely and leave NavigationHistory with no entries.
+        // This check here is to prevent crashing in that scenario.
+        if (history.getEntryCount() == 0) return;
+
+        NavigationEntry entry = history.getEntryAtIndex(history.getCurrentEntryIndex());
+        if (SearchUrlHelper.isSrpUrl(entry.getUrl())) {
+            if (entry.getUrl().equals(mLastSrpUrl)) {
+                // Treat re-navigation to the last seen SRP as a back navigation.
+                mBackNavigationCount++;
+            } else {
+                // Encountered a new SRP session. Record the previous session and start a new one.
+                recordMetricAndClearCache();
+                mLastSrpUrl = entry.getUrl();
+            }
+            // A page opened through SRP has google.com as its referrer URL. Treat other cases as
+            // navigating away from the SRP session.
+        } else if (!SearchUrlHelper.isGoogleDomainUrl(entry.getReferrerUrl())) {
+            recordMetricAndClearCache();
+        }
+        mLastVisitedUrl = entry.getUrl();
+    }
+
+    @Override
+    public void onContentChanged(Tab tab) {
+        if (tab.isNativePage()) {
+            recordMetricAndClearCache();
+        }
+    }
+
+    @Override
+    public void onHidden(Tab tab, int reason) {
+        if (reason == TabHidingType.ACTIVITY_HIDDEN) {
+            recordMetricAndClearCache();
+        }
+    }
+
+    @Override
+    public void onDestroyed(Tab tab) {
+        recordMetricAndClearCache();
+        tab.removeObserver(this);
+    }
+
+    private void recordMetricAndClearCache() {
+        if (mLastSrpUrl != null) {
+            RecordHistogram.recordCount100Histogram(
+                    "Browser.ContinuousSearch.BackNavigationToSrp", mBackNavigationCount);
+        }
+        mLastSrpUrl = null;
+        mBackNavigationCount = 0;
+    }
+}

chrome/browser/continuous_search/internal/android/java/src/org/chromium/chrome/browser/continuous_search/SearchUrlHelper.java

@@ -15,6 +15,26 @@ import org.chromium.url.GURL;
 public class SearchUrlHelper {
     private SearchUrlHelper() {}
 
+    /**
+     * Checks whether the provided url is valid, the host is "www.google.<TLD>" with a valid TLD and
+     * has an HTTP or HTTPS scheme. Returns false if the url doesn't use the standard port for its
+     * scheme (80 for HTTP, 443 for HTTPS).
+     * @param url the url to check the criteria against.
+     * @return true if url satisfies all the requirements above.
+     */
+    public static boolean isGoogleDomainUrl(GURL url) {
+        return SearchUrlHelperJni.get().isGoogleDomainUrl(url);
+    }
+
+    /**
+     * Checks whether the provided url represents a valid Google search url.
+     * @param url the url to check.
+     * @return true if the url satisfies the criteria.
+     */
+    public static boolean isSrpUrl(GURL url) {
+        return SearchUrlHelperJni.get().isSrpUrl(url);
+    }
+
     /**
      * Gets the query of the provided url if it is a SRP URL.
      * @param url The url to try to extract the query from.
@@ -26,6 +46,8 @@ public class SearchUrlHelper {
 
     @NativeMethods
     interface Natives {
+        boolean isGoogleDomainUrl(GURL url);
+        boolean isSrpUrl(GURL url);
         String getQueryIfSrpUrl(GURL url);
     }
 }

chrome/browser/continuous_search/internal/search_url_helper.cc

@@ -18,6 +18,26 @@
 
 namespace continuous_search {
 
+jboolean JNI_SearchUrlHelper_IsGoogleDomainUrl(
+    JNIEnv* env,
+    const base::android::JavaParamRef<jobject>& j_gurl) {
+  std::unique_ptr<GURL> url = url::GURLAndroid::ToNativeGURL(env, j_gurl);
+  if (!url->is_valid())
+    return false;
+  return static_cast<jboolean>(
+      google_util::IsGoogleDomainUrl(*url, google_util::DISALLOW_SUBDOMAIN,
+                                     google_util::DISALLOW_NON_STANDARD_PORTS));
+}
+
+jboolean JNI_SearchUrlHelper_IsSrpUrl(
+    JNIEnv* env,
+    const base::android::JavaParamRef<jobject>& j_gurl) {
+  std::unique_ptr<GURL> url = url::GURLAndroid::ToNativeGURL(env, j_gurl);
+  if (!url->is_valid())
+    return false;
+  return static_cast<jboolean>(google_util::IsGoogleSearchUrl(*url));
+}
+
 base::android::ScopedJavaLocalRef<jstring> JNI_SearchUrlHelper_GetQueryIfSrpUrl(
     JNIEnv* env,
     const base::android::JavaParamRef<jobject>& j_gurl) {

tools/metrics/histograms/histograms_xml/browser/histograms.xml

@@ -52,6 +52,21 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
+<histogram name="Browser.ContinuousSearch.BackNavigationToSrp" units="count"
+    expires_after="2021-06-20">
+  <owner>ckitagawa@chromium.org</owner>
+  <owner>fredmello@chromium.org</owner>
+  <owner>mahmoudi@chromium.org</owner>
+  <owner>yashard@chromium.org</owner>
+  <summary>
+    Records the number of back navigations to the Google search result page
+    while in a search session. It is emitted when the session is considered
+    ended. Different actions that cause the search session to end include
+    navigating away from SRP (or one on the pages linked in SRP), closing the
+    SRP tab and closing the browser.
+  </summary>
+</histogram>
+
 <histogram name="Browser.DarkModeStatus" enum="DarkModeStatus"
     expires_after="2021-06-27">
   <owner>lgrey@chromium.org</owner>