Plumb flag and settings for BlinkGenPropertyTrees finch trial

This patch plumbs a flag and settings for a BlinkGenPropertyTrees
finch trial. Because we have dependencies on the existing command line
flag (--enable-blink-gen-property-trees), the command line flag has not
been removed in this patch but will be removed in a followup.

Bug: 836884
Change-Id: I73d4c01964b953397d1857a9ee130502792b3d4a
Reviewed-on: https://chromium-review.googlesource.com/c/1355852
Reviewed-by: Kentaro Hara <[email protected]>
Reviewed-by: Avi Drissman <[email protected]>
Reviewed-by: Xianzhu Wang <[email protected]>
Commit-Queue: Avi Drissman <[email protected]>
Cr-Commit-Position: refs/heads/master@{#612951}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index f5a2b84..93eff49a 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -3868,6 +3868,11 @@
      flag_descriptions::kLayeredAPIDescription, kOsAll,
      FEATURE_VALUE_TYPE(features::kLayeredAPI)},
 
+    {"enable-blink-gen-property-trees",
+     flag_descriptions::kEnableBlinkGenPropertyTreesName,
+     flag_descriptions::kEnableBlinkGenPropertyTreesDescription, kOsAll,
+     FEATURE_VALUE_TYPE(blink::features::kBlinkGenPropertyTrees)},
+
     {"enable-layout-ng", flag_descriptions::kEnableLayoutNGName,
      flag_descriptions::kEnableLayoutNGDescription, kOsAll,
      FEATURE_VALUE_TYPE(blink::features::kLayoutNG)},