✉️  Add flag for TWA PostMessage.

Also removes CCTPostMessageOrigin as that will be launched alongside
TrustedWebActivityPostMessage so this simplifies things.

Bug: 1418044
Change-Id: Iedff32a12817c5d62c224251c3e6da27ec2cd00a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4439695
Commit-Queue: Peter Beverloo <[email protected]>
Code-Coverage: Findit <[email protected]>
Reviewed-by: Peter Beverloo <[email protected]>
Auto-Submit: Peter Conn <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1134625}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index 8dfcdda6..3dc186c 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -4304,6 +4304,11 @@
     "Controls whether the Translate Message UI will be shown instead of the "
     "Translate InfoBar.";
 
+const char kTwaPostMessageName[] = "PostMessage for Trusted Web Activities";
+const char kTwaPostMessageDescription[] =
+    "Enables PostMessage between the "
+    "shell app and the web page in Trusted Web Activities.";
+
 const char kUpdateMenuBadgeName[] = "Force show update menu badge";
 const char kUpdateMenuBadgeDescription[] =
     "When enabled, a badge will be shown on the app menu button if the update "