[CrOS WebAPKs] Add chrome://flags entry for Arc to Web app sharing

We have an existing base::Feature to control whether ARC apps should
be allowed to share content to web apps. This CL adds a flag entry
for this feature, to assist with testing.

Bug: b/178656389
Change-Id: I913298a7cb242411068f9e49f9d2ef65632c989a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2952752
Commit-Queue: Tim Sergeant <[email protected]>
Reviewed-by: Melissa Zhang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#891561}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index 629a13b..926b51a 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -3889,6 +3889,12 @@
     "Allow Android to use high-memory dalvik profile when applicable for "
     "high-memory devices.";
 
+const char kArcWebAppShareName[] = "Enable sharing to Web Apps from ARC";
+const char kArcWebAppShareDescription[] =
+    "Allow Android apps to send shared text and files to web apps. When "
+    "disabled, web apps may still appear in share sheets, but will not "
+    "receive any shared content.";
+
 const char kArcEnableUsapName[] =
     "Enable ARC Unspecialized Application Processes";
 const char kArcEnableUsapDesc[] =