Satisfy Finch requirements for RenderBlockingFullFrameRate on WebView

Bug: 397832388
Change-Id: I68dd2d32a40cfe79334846faa85c802264124f77
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6440001
Commit-Queue: Jiacheng Guo <gjc@google.com>
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1445663}

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

@@ -1091,6 +1091,10 @@ public final class ProductionSupportedFlagList {
                 AwFeatures.WEBVIEW_SEQUENCED_SHOULD_INTERCEPT_REQUEST,
                 "Enforces sequencing of calls to shouldInterceptRequest, "
                         + "instead of invoking each call on a separate background thread."),
+        Flag.baseFeature(
+                BlinkFeatures.RENDER_BLOCKING_FULL_FRAME_RATE,
+                "Enable the <link blocking=\"full-frame-rate\"/> API to lower the frame rate during"
+                        + " loading"),
         // Add new commandline switches and features above. The final entry should have a
         // trailing comma for cleaner diffs.
     };