Don't crash when two extension uninstall prompts are shown at the same time.

chrome/browser/extensions/api/management/management_api.cc

Index: chrome/browser/extensions/api/management/management_api.cc
diff --git a/chrome/browser/extensions/api/management/management_api.cc b/chrome/browser/extensions/api/management/management_api.cc
index 86f67ef9684dfffc23e434167800577d11766a4e..fa6a0ffd5c0cc6b5de5566a9d54a15b324fb5692 100644
--- a/chrome/browser/extensions/api/management/management_api.cc
+++ b/chrome/browser/extensions/api/management/management_api.cc
@@ -580,13 +580,22 @@ void ManagementUninstallFunctionBase::SetAutoConfirmForTest(
 
 void ManagementUninstallFunctionBase::Finish(bool should_uninstall) {
   if (should_uninstall) {
-    bool success = service()->UninstallExtension(
-        extension_id_,
-        false, /* external uninstall */
-        NULL);
+    // The extension can be uninstalled in another window while the UI was
+    // showing. Do nothing in that case.

[not at google - send to devlin, 2014/05/16 22:11:00]

Do we have any tests which actually exercise the UI behaviour of the uninstall
dialogue? If so could you update it? If not I expect it will be a PITA so don't
worry.

[Marijn Kruisselbrink, 2014/05/16 22:19:12]

I think in tests we bypass the dialog, and behave as if either accept or cancel
was clicked synchronously. So exercising the actual UI in tests is going to be a
PITA.

+    ExtensionRegistry* registry = ExtensionRegistry::Get(GetProfile());
+    const Extension* extension = registry->GetExtensionById(
+        extension_id_, ExtensionRegistry::EVERYTHING);
+    if (!extension) {

[not at google - send to devlin, 2014/05/16 22:11:00]

emulate the extension not being there by using kNoExtensionError? (see line 540
for example).

[Marijn Kruisselbrink, 2014/05/16 22:19:12]

Done.

+      SendResponse(false);
+    } else {
+      bool success =
+          service()->UninstallExtension(extension_id_,

[not at google - send to devlin, 2014/05/16 22:11:00]

what kind of behaviour do we have in ExtensionService::UninstallExtension if the
extension isn't there? can we make sure it's a CHECK failure rather than some
kind of unexpected failure.

speaking of which, what does the chrome://extensions page do when the extension
gets uninstalled underneath it?

[Marijn Kruisselbrink, 2014/05/16 22:19:12]

It is a CHECK failure already.
chrome://extensions does exactly what I did here. If you try to uninstall the
same extension twice, the second time clicking accept will just silently do
nothing.

+                                        false, /* external uninstall */
+                                        NULL);
 
-    // TODO set error_ if !success
-    SendResponse(success);
+      // TODO set error_ if !success
+      SendResponse(success);
+    }
   } else {
     error_ = ErrorUtils::FormatErrorMessage(
         keys::kUninstallCanceledError, extension_id_);