Revert of Disable ExternalPopupMenuRemoveTest.RemoveOnChange. (patchset #1 id:1 of https://codereview.chromium.org/1271223002/ )

Reason for revert:
Reverted Blink r200000.

Original issue's description:
> Disable ExternalPopupMenuRemoveTest.RemoveOnChange.
>
> The behavior was intentionally changed by Blink r200000 [1].
>
> [1] https://src.chromium.org/viewvc/blink?revision=200000&view=revision
>
> BUG=516945
> [email protected],[email protected]
> NOTRY=true
>
> Committed: https://crrev.com/372de78e05c538ae724563ee107e47fbd17498d4
> Cr-Commit-Position: refs/heads/master@{#341867}

[email protected],[email protected]
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=516945

Review URL: https://codereview.chromium.org/1274813005

Cr-Commit-Position: refs/heads/master@{#341991}
diff --git a/content/renderer/external_popup_menu_browsertest.cc b/content/renderer/external_popup_menu_browsertest.cc
index 675d915..885070e 100644
--- a/content/renderer/external_popup_menu_browsertest.cc
+++ b/content/renderer/external_popup_menu_browsertest.cc
@@ -138,8 +138,7 @@
 
 // Tests that nothing bad happen when the page removes the select when it
 // changes. (http://crbug.com/61997)
-// TODO(tkent): Change event becomes asynchronous.  crbug.com/516945
-TEST_F(ExternalPopupMenuRemoveTest, DISABLED_RemoveOnChange) {
+TEST_F(ExternalPopupMenuRemoveTest, RemoveOnChange) {
   // Click the text field once to show the popup.
   EXPECT_TRUE(SimulateElementClick(kSelectID));