[Tab Switcher] Default enable deferred tab switcher creation

Default to lazily initializing the tab switcher at startup. This
improves memory usage and jankiness at startup.

See bug for metrics analysis.

Bug: b/40932816
Change-Id: Ia8e4a32250b43edb7a374719ffe54bd81a74b7b2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5287976
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Commit-Queue: Calder Kitagawa <ckitagawa@chromium.org>
Reviewed-by: Sky Malice <skym@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1259526}

chrome/android/javatests/src/org/chromium/chrome/browser/toolbar/top/ToolbarPhoneTest.java

@@ -748,7 +748,11 @@ public class ToolbarPhoneTest {
     @Test
     @MediumTest
     @EnableFeatures(ChromeFeatureList.TAB_TO_GTS_ANIMATION)
-    @DisableFeatures({ChromeFeatureList.START_SURFACE_ANDROID, ChromeFeatureList.ANDROID_HUB})
+    @DisableFeatures({
+        ChromeFeatureList.START_SURFACE_ANDROID,
+        ChromeFeatureList.ANDROID_HUB,
+        ChromeFeatureList.DEFER_TAB_SWITCHER_LAYOUT_CREATION
+    })
     @DisableAnimationsTestRule.EnsureAnimationsOn
     public void testToolbarTabSwitcherButtonNotClickableDuringTransition_startSurfaceDisabled() {
         ChromeTabbedActivity cta = mActivityTestRule.getActivity();

chrome/browser/flags/android/chrome_feature_list.cc

@@ -594,7 +594,7 @@ BASE_FEATURE(kDeferNotifyInMotion,
 
 BASE_FEATURE(kDeferTabSwitcherLayoutCreation,
              "DeferTabSwitcherLayoutCreation",
-             base::FEATURE_DISABLED_BY_DEFAULT);
+             base::FEATURE_ENABLED_BY_DEFAULT);
 
 BASE_FEATURE(kDelayTempStripRemoval,
              "DelayTempStripRemoval",

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

@@ -552,7 +552,7 @@ public abstract class ChromeFeatureList {
     public static final CachedFlag sCommandLineOnNonRooted =
             newCachedFlag(COMMAND_LINE_ON_NON_ROOTED, false);
     public static final CachedFlag sDeferTabSwitcherLayoutCreation =
-            newCachedFlag(DEFER_TAB_SWITCHER_LAYOUT_CREATION, false);
+            newCachedFlag(DEFER_TAB_SWITCHER_LAYOUT_CREATION, true);
     public static final CachedFlag sDelayTempStripRemoval =
             newCachedFlag(DELAY_TEMP_STRIP_REMOVAL, true);
     public static final CachedFlag sDragDropIntoOmnibox =

testing/variations/fieldtrial_testing_config.json

@@ -5663,21 +5663,6 @@
             ]
         }
     ],
-    "DeferTabSwitcherLayoutCreation": [
-        {
-            "platforms": [
-                "android"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled",
-                    "enable_features": [
-                        "DeferTabSwitcherLayoutCreation"
-                    ]
-                }
-            ]
-        }
-    ],
     "DeferredOverlayRelease": [
         {
             "platforms": [