Ship HTMLDialogElement

Intent-to-ship:
https://groups.google.com/a/chromium.org/d/msg/blink-dev/Ae18uqxjzp8/C4K_J1xpnGwJ

BUG=140205

Review URL: https://codereview.chromium.org/330873002

git-svn-id: svn://svn.chromium.org/blink/trunk@176133 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/virtual/stable/webexposed/global-constructors-listing-expected.txt

@@ -110,6 +110,7 @@ HTMLCollection
 HTMLContentElement
 HTMLDListElement
 HTMLDataListElement
+HTMLDialogElement
 HTMLDirectoryElement
 HTMLDivElement
 HTMLDocument

third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in

@@ -49,7 +49,7 @@ CSS3TextDecorations status=experimental
 CustomSchemeHandler depends_on=NavigatorContentUtils, status=experimental
 Database status=stable
 DeviceLight status=test
-DialogElement status=experimental
+DialogElement status=stable
 EncodingAPI status=experimental
 EncryptedMedia status=test
 EncryptedMediaAnyVersion status=stable