Fix crash by preventing extensions from changing their IDs.

chrome/browser/extensions/extension_service.cc

Index: chrome/browser/extensions/extension_service.cc
diff --git a/chrome/browser/extensions/extension_service.cc b/chrome/browser/extensions/extension_service.cc
index d8b7f5f35c5ca7b80afc638c826921d1e09cfb5e..7af3d58a2252f75e60fd69f4864e760d571c2093 100644
--- a/chrome/browser/extensions/extension_service.cc
+++ b/chrome/browser/extensions/extension_service.cc
@@ -1428,6 +1428,15 @@ void ExtensionService::LoadInstalledExtension(const ExtensionInfo& info,
     error = errors::kManifestUnreadable;
   }
 
+  // Once installed, non-unpacked extensions cannot change their IDs (e.g., by
+  // updating the 'key' field in their manifest).
+  if (extension &&
+      extension->location() != Extension::LOAD &&
+      info.extension_id != extension->id()) {
+    error = errors::kCannotChangeExtensionID;
+    extension = NULL;

[asargent_no_longer_on_chrome, 2011/09/26 22:08:04]

It might be good to include a uma histogram here, so you could measure if this
is ever actually happening in the field. 

[jstritar, 2011/09/26 22:11:03]

Agreed. Do you think we should add a one off histogram here or collect a
histogram for extension load errors more generally in another CL?

+  }
+
   if (!extension) {
     ReportExtensionLoadError(info.extension_path,
                              error,