Remove CRX2 parsers from Chrome.

Unwinds some now-dead policy handling.
Repackages some remaining CRX2 items into CRX3.
  Where they had no keys checked in, I created keys are rotated IDs.
  For the component updater, I also had to change hash/size constants.
Removes a kiosk browsertest that verified CRX2 compatibility.

Bug: 740715
Change-Id: I3f96ff682400c509ba3050310c3ada3fcf552360
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1729917
Commit-Queue: Joshua Pawlicki <[email protected]>
Reviewed-by: Sergey Poromov <[email protected]>
Reviewed-by: Dominic Battré <[email protected]>
Reviewed-by: Denis Kuznetsov <[email protected]>
Reviewed-by: Alexander Alekseev <[email protected]>
Reviewed-by: proberge <[email protected]>
Reviewed-by: Devlin <[email protected]>
Reviewed-by: John Chen <[email protected]>
Auto-Submit: Joshua Pawlicki <[email protected]>
Cr-Commit-Position: refs/heads/master@{#692756}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index c12716e7..21d003f 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -486,6 +486,9 @@
 #endif
 
 // Deprecated 8/2019
+const char kInsecureExtensionUpdatesEnabled[] =
+    "extension_updates.insecure_extension_updates_enabled";
+
 const char kLastStartupTimestamp[] = "startup_metric.last_startup_timestamp";
 
 // Deprecated 8/2019
@@ -564,6 +567,8 @@
   registry->RegisterIntegerPref(kLocalProfileId, 0);
 #endif
 
+  registry->RegisterBooleanPref(kInsecureExtensionUpdatesEnabled, false);
+
   registry->RegisterDictionaryPref(kHintLoadedCounts);
 }
 
@@ -1167,6 +1172,7 @@
   profile_prefs->ClearPref(kLocalProfileId);
 #endif
 
-  // Added 8/2019.
+  // Added 8/2019
+  profile_prefs->ClearPref(kInsecureExtensionUpdatesEnabled);
   profile_prefs->ClearPref(kHintLoadedCounts);
 }