[Paint Preview] Add capture experiment

This implements the logic for the paint preview capture experiment.
The experiment is behind a chrome flag that is disabled by default.
Experiment doc: http://go/fdt-sample-experiment

Bug: 1039810
Change-Id: I0b9db1ebe06d5b10da482ca1105c88d33afd1bc4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2044064Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Reviewed-by: Theresa  <twellington@chromium.org>
Commit-Queue: Mehran Mahmoudi <mahmoudi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#743392}

chrome/android/chrome_java_sources.gni

@@ -1211,6 +1211,8 @@ chrome_java_sources = [
   "java/src/org/chromium/chrome/browser/page_info/PermissionParamsListBuilder.java",
   "java/src/org/chromium/chrome/browser/page_info/SiteSettingsHelper.java",
   "java/src/org/chromium/chrome/browser/page_info/SystemSettingsActivityRequiredListener.java",
+  "java/src/org/chromium/chrome/browser/paint_preview/PaintPreviewExperiments.java",
+  "java/src/org/chromium/chrome/browser/paint_preview/PaintPreviewTabHelper.java",
   "java/src/org/chromium/chrome/browser/partnerbookmarks/PartnerBookmark.java",
   "java/src/org/chromium/chrome/browser/partnerbookmarks/PartnerBookmarksFaviconThrottle.java",
   "java/src/org/chromium/chrome/browser/partnerbookmarks/PartnerBookmarksProviderIterator.java",

chrome/android/java/src/org/chromium/chrome/browser/flags/CachedFeatureFlags.java

@@ -390,7 +390,7 @@ public class CachedFeatureFlags {
     }
 
     /**
-     * @return Whether the Paint Preview tapture test is enabled
+     * @return Whether the Paint Preview capture test is enabled.
      */
     public static boolean isPaintPreviewTestEnabled() {
         return isEnabled(ChromeFeatureList.PAINT_PREVIEW_TEST);

chrome/android/java/src/org/chromium/chrome/browser/paint_preview/OWNERS

+file://components/paint_preview/OWNERS
+# COMPONENT: Internals>FreezeDriedTabs

chrome/android/java/src/org/chromium/chrome/browser/paint_preview/PaintPreviewExperiments.java

+// Copyright 2020 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.paint_preview;
+
+import org.chromium.base.library_loader.LibraryLoader;
+import org.chromium.chrome.browser.flags.ChromeFeatureList;
+import org.chromium.components.paintpreview.browser.PaintPreviewUtils;
+import org.chromium.content_public.browser.WebContents;
+
+import java.util.Random;
+
+/**
+ * Contains experiments related to the Paint Preview feature.
+ */
+public class PaintPreviewExperiments {
+    private static Random sRandom = new Random();
+
+    /**
+     * Param name for field trial param that determines capture experiment trigger probability
+     * threshold.
+     **/
+    private static final String CAPTURE_EXPERIMENT_TRIGGER_PROBABILITY_THRESHOLD =
+            "capture_trigger_probability_threshold";
+
+    /**
+     * Runs the Paint Preview capture experiment if the experiment is enabled and a probability
+     * threshold is met. The probability threshold is determined by a field trial param.
+     * @param contents The WebContents of the page to capture.
+     */
+    public static void runCaptureExperiment(WebContents contents) {
+        // ChromeFeatureList and the Paint Preview component rely on native.
+        if (!LibraryLoader.getInstance().isInitialized()) {
+            return;
+        }
+
+        if (!ChromeFeatureList.isEnabled(ChromeFeatureList.PAINT_PREVIEW_CAPTURE_EXPERIMENT)) {
+            return;
+        }
+
+        double captureTriggerProbabilityThreshold =
+                ChromeFeatureList.getFieldTrialParamByFeatureAsDouble(
+                        ChromeFeatureList.PAINT_PREVIEW_CAPTURE_EXPERIMENT,
+                        CAPTURE_EXPERIMENT_TRIGGER_PROBABILITY_THRESHOLD, 0);
+        if (sRandom.nextDouble() >= captureTriggerProbabilityThreshold) {
+            return;
+        }
+
+        PaintPreviewUtils.capturePaintPreview(contents);
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/paint_preview/PaintPreviewTabHelper.java

+// Copyright 2020 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.paint_preview;
+
+import org.chromium.chrome.browser.tab.EmptyTabObserver;
+import org.chromium.chrome.browser.tab.Tab;
+import org.chromium.content_public.browser.NavigationHandle;
+
+/**
+ * Manages the Paint Preview component for a given {@link Tab}. Destroyed together with the tab.
+ */
+public class PaintPreviewTabHelper extends EmptyTabObserver {
+    public static void createForTab(Tab tab) {
+        new PaintPreviewTabHelper(tab);
+    }
+
+    private PaintPreviewTabHelper(Tab tab) {
+        tab.addObserver(this);
+    }
+
+    @Override
+    public void onDestroyed(Tab tab) {
+        tab.removeObserver(this);
+    }
+
+    @Override
+    public void onDidFinishNavigation(Tab tab, NavigationHandle navigationHandle) {
+        if (qualifiesForCapture(tab)) {
+            PaintPreviewExperiments.runCaptureExperiment(tab.getWebContents());
+        }
+    }
+
+    /**
+     * Checks whether a given {@link Tab} qualifies for Paint Preview capture.
+     */
+    private boolean qualifiesForCapture(Tab tab) {
+        return !tab.isIncognito() && !tab.isNativePage() && !tab.isShowingErrorPage()
+                && tab.getWebContents() != null;
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/tab/DEPS

@@ -5,6 +5,7 @@ include_rules = [
   "+chrome/android/java/src/org/chromium/chrome/browser/TabHidingType.java",
   "+chrome/android/java/src/org/chromium/chrome/browser/flags/ChromeFeatureList.java",
   "+chrome/android/java/src/org/chromium/chrome/browser/incognito/IncognitoUtils.java",
+  "+chrome/android/java/src/org/chromium/chrome/browser/paint_preview/PaintPreviewTabHelper.java",
   "+chrome/android/java/src/org/chromium/chrome/browser/previews/Previews.java",
   "+chrome/android/java/src/org/chromium/chrome/browser/ssl/SecurityStateModel.java",
   "+chrome/android/java/src/org/chromium/chrome/browser/tab",

chrome/android/java/src/org/chromium/chrome/browser/tab/TabHelpers.java

@@ -13,6 +13,7 @@ import org.chromium.chrome.browser.dom_distiller.TabDistillabilityProvider;
 import org.chromium.chrome.browser.flags.ChromeFeatureList;
 import org.chromium.chrome.browser.infobar.InfoBarContainer;
 import org.chromium.chrome.browser.media.ui.MediaSessionTabHelper;
+import org.chromium.chrome.browser.paint_preview.PaintPreviewTabHelper;
 import org.chromium.chrome.browser.tab.TabUma.TabCreationState;
 import org.chromium.chrome.browser.tasks.TaskRecognizer;
 import org.chromium.content_public.browser.SelectionPopupController;
@@ -44,6 +45,7 @@ public final class TabHelpers {
         MediaSessionTabHelper.createForTab(tab);
         TaskTabHelper.createForTab(tab, parentTab);
         TabBrowserControlsConstraintsHelper.createForTab(tab);
+        PaintPreviewTabHelper.createForTab(tab);
 
         // TODO(jinsukkim): Do this by having something observe new tab creation.
         if (tab.isIncognito()) CipherFactory.getInstance().triggerKeyGeneration();

chrome/browser/flags/android/chrome_feature_list.cc

@@ -212,6 +212,7 @@ const base::Feature* kFeaturesExposedToJava[] = {
     &kWebApkAdaptiveIcon,
     &net::features::kSameSiteByDefaultCookies,
     &net::features::kCookiesWithoutSameSiteMustBeSecure,
+    &paint_preview::kPaintPreviewCaptureExperiment,
     &paint_preview::kPaintPreviewTest,
     &payments::features::kAlwaysAllowJustInTimePaymentApp,
     &payments::features::kPaymentRequestSkipToGPay,

chrome/browser/flags/android/java/src/org/chromium/chrome/browser/flags/ChromeFeatureList.java

@@ -305,6 +305,7 @@ public abstract class ChromeFeatureList {
     public static final String OMNIBOX_SEARCH_ENGINE_LOGO = "OmniboxSearchEngineLogo";
     public static final String OVERLAY_NEW_LAYOUT = "OverlayNewLayout";
     public static final String OVERSCROLL_HISTORY_NAVIGATION = "OverscrollHistoryNavigation";
+    public static final String PAINT_PREVIEW_CAPTURE_EXPERIMENT = "PaintPreviewCaptureExperiment";
     public static final String PAINT_PREVIEW_TEST = "PaintPreviewTest";
     public static final String PASSWORD_EDITING_ANDROID = "PasswordEditingAndroid";
     public static final String PASSWORD_MANAGER_ONBOARDING_ANDROID =

components/paint_preview/features/features.cc

@@ -8,6 +8,8 @@
 
 namespace paint_preview {
 
+const base::Feature kPaintPreviewCaptureExperiment{
+    "PaintPreviewCaptureExperiment", base::FEATURE_DISABLED_BY_DEFAULT};
 const base::Feature kPaintPreviewTest{"PaintPreviewTest",
                                       base::FEATURE_DISABLED_BY_DEFAULT};
 

components/paint_preview/features/features.h

@@ -9,10 +9,17 @@
 
 namespace paint_preview {
 
+// Used to enable the paint preview capture experiment on Android. If enabled,
+// paint preview capture will be triggered for a fraction of page loads, with
+// accordance to a probability threshold that is set by a field trial param.
+// Metrics for the capture are logged and the resulting paint preview is then
+// deleted.
+extern const base::Feature kPaintPreviewCaptureExperiment;
+
 // Used to enable a main menu item on Android that captures a paint preview for
-// the current page. Metrics for the capture are logged and a toast is raised.
-// The resulting paint preview is then deleted. This intended to test whether
-// capturing works on a specific site.
+// the current page. Metrics for the capture are logged. The resulting paint
+// preview is then deleted. This intended to test whether capturing works on a
+// specific site.
 extern const base::Feature kPaintPreviewTest;
 
 }  // namespace paint_preview