[LCPP] Enable LCPTimingPredictorPrerender2 on WebView in field trial

Bug: 325124210
Change-Id: Ica1390f26690b905e6743e1432fd3394fa1263a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5960162
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Auto-Submit: Yoichi Osato <yoichio@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1374452}

android_webview/java/src/org/chromium/android_webview/common/ProductionSupportedFlagList.java

@@ -1097,6 +1097,10 @@ public final class ProductionSupportedFlagList {
                 "AsyncFastCheckout", "When enabled, run FastCheckoutTabHelper asynchronously."),
         Flag.baseFeature("Prerender2FallbackPrefetchSpecRules"),
         Flag.baseFeature("PrefetchReusable"),
+        Flag.baseFeature(
+                "LCPTimingPredictorPrerender2",
+                "When enabled, Prerender2 by Speculation Rules API is delayed until LCP is"
+                        + " finished."),
         // Add new commandline switches and features above. The final entry should have a
         // trailing comma for cleaner diffs.
     };

testing/variations/fieldtrial_testing_config.json

@@ -13171,6 +13171,7 @@
         {
             "platforms": [
                 "android",
+                "android_webview",
                 "chromeos",
                 "chromeos_lacros",
                 "linux",