Bug 1490414: Add #includes to fix non-unified build bustage in layout/generic. r=TYLin

- We need nsIContentInlines.h to provide the (inline) nsIContent::GetShadowRoot definition.
- We need ShadowRoot.h to allow dereferencing of the pointer that GetShadowRoot() returns.

Differential Revision: https://phabricator.services.mozilla.com/D5564

--HG--
extra : moz-landing-system : lando

layout/generic/nsVideoFrame.cpp

@@ -12,6 +12,7 @@
 #include "nsGkAtoms.h"
 
 #include "mozilla/dom/HTMLVideoElement.h"
+#include "mozilla/dom/ShadowRoot.h"
 #include "mozilla/layers/WebRenderLayerManager.h"
 #include "nsDisplayList.h"
 #include "nsGenericHTMLElement.h"
@@ -19,6 +20,7 @@
 #include "nsContentCreatorFunctions.h"
 #include "nsBoxLayoutState.h"
 #include "nsBoxFrame.h"
+#include "nsIContentInlines.h"
 #include "nsImageFrame.h"
 #include "nsIImageLoadingContent.h"
 #include "nsContentUtils.h"