[Feed] Set USE_TIMEOUT_SCHEDULER.

When the NTP was open and an article fetch completed, it would cause
the list of articles to flicker and be completely replaced. This change
removes the flicker, and only articles below the edge of the screen are
replaced.

Bug: 911489
Change-Id: Id87b221e142533a0bf448a0efe2cdcdf43209dc0
Reviewed-on: https://chromium-review.googlesource.com/c/1363959
Commit-Queue: Sky Malice <skym@chromium.org>
Reviewed-by: Filip Gorski <fgorski@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614790}

chrome/android/feed/core/java/src/org/chromium/chrome/browser/feed/FeedConfiguration.java

@@ -59,6 +59,10 @@ public final class FeedConfiguration {
     /** Default value for triggering immediate pagination. */
     public static final boolean TRIGGER_IMMEDIATE_PAGINATION_DEFAULT = false;
 
+    private static final String USE_TIMEOUT_SCHEDULER = "use_timeout_scheduler";
+    /** Default value for the type of scheduler handling. */
+    public static final boolean USE_TIMEOUT_SCHEDULER_DEFAULT = true;
+
     private static final String VIEW_LOG_THRESHOLD = "view_log_threshold";
     /** Default value for logging view threshold. */
     public static final double VIEW_LOG_THRESHOLD_DEFAULT = 0.66d;
@@ -139,6 +143,17 @@ public final class FeedConfiguration {
                 TRIGGER_IMMEDIATE_PAGINATION_DEFAULT);
     }
 
+    /**
+     * @return Whether the Feed's session handling should use logic to deal with timeouts and
+     * placing new results below the fold.
+     */
+    @VisibleForTesting
+    static boolean getUseTimeoutScheduler() {
+        return ChromeFeatureList.getFieldTrialParamByFeatureAsBoolean(
+                ChromeFeatureList.INTEREST_FEED_CONTENT_SUGGESTIONS, USE_TIMEOUT_SCHEDULER,
+                USE_TIMEOUT_SCHEDULER_DEFAULT);
+    }
+
     /** @return How much of a card must be on screen to generate a UMA log view. */
     @VisibleForTesting
     static double getViewLogThreshold() {
@@ -166,6 +181,7 @@ public final class FeedConfiguration {
                 .put(ConfigKey.SESSION_LIFETIME_MS, FeedConfiguration.getSessionLifetimeMs())
                 .put(ConfigKey.TRIGGER_IMMEDIATE_PAGINATION,
                         FeedConfiguration.getTriggerImmediatePagination())
+                .put(ConfigKey.USE_TIMEOUT_SCHEDULER, FeedConfiguration.getUseTimeoutScheduler())
                 .put(ConfigKey.VIEW_LOG_THRESHOLD, FeedConfiguration.getViewLogThreshold())
                 .build();
     }

chrome/android/javatests/src/org/chromium/chrome/browser/feed/FeedConfigurationTest.java

@@ -51,6 +51,7 @@ public class FeedConfigurationTest {
         Assert.assertEquals(FeedConfiguration.SESSION_LIFETIME_MS_DEFAULT,
                 FeedConfiguration.getSessionLifetimeMs());
         Assert.assertFalse(FeedConfiguration.getTriggerImmediatePagination());
+        Assert.assertTrue(FeedConfiguration.getUseTimeoutScheduler());
         Assert.assertEquals(FeedConfiguration.VIEW_LOG_THRESHOLD_DEFAULT,
                 FeedConfiguration.getViewLogThreshold(), ASSERT_EQUALS_DOUBLE_DELTA);
     }
@@ -142,6 +143,16 @@ public class FeedConfigurationTest {
         Assert.assertTrue(FeedConfiguration.getTriggerImmediatePagination());
     }
 
+    @Test
+    @Feature({"Feed"})
+    @CommandLineFlags.
+    Add({"enable-features=InterestFeedContentSuggestions<Trial", "force-fieldtrials=Trial/Group",
+            "force-fieldtrial-params=Trial.Group:use_timeout_scheduler/false"})
+    public void
+    testUseTimeoutScheduler() {
+        Assert.assertFalse(FeedConfiguration.getUseTimeoutScheduler());
+    }
+
     @Test
     @Feature({"Feed"})
     @CommandLineFlags.
@@ -177,6 +188,7 @@ public class FeedConfigurationTest {
                 configuration.getValueOrDefault(ConfigKey.SESSION_LIFETIME_MS, 0l));
         Assert.assertFalse(
                 configuration.getValueOrDefault(ConfigKey.TRIGGER_IMMEDIATE_PAGINATION, true));
+        Assert.assertTrue(configuration.getValueOrDefault(ConfigKey.USE_TIMEOUT_SCHEDULER, false));
         Assert.assertEquals(Double.valueOf(FeedConfiguration.VIEW_LOG_THRESHOLD_DEFAULT),
                 configuration.getValueOrDefault(ConfigKey.VIEW_LOG_THRESHOLD, 0d),
                 ASSERT_EQUALS_DOUBLE_DELTA);