Bug 1730774 part 3: Add includes for Inlines headers, to fix non-unified-build linking issues in layout/generic (and remove REQUIRES_UNIFIED_BUILD decl). r=TYLin

After the fixes in this patch, the REQUIRES_UNIFIED_BUILD declaration is no
longer needed, so I'm removing it here.  This directory now builds successfully
with that removed and with ac_add_options --disable-unified-build in the
mozconfig.

Differential Revision: https://phabricator.services.mozilla.com/D125738

layout/generic/moz.build

@@ -270,5 +270,3 @@ if CONFIG["MOZ_WIDGET_TOOLKIT"] == "gtk":
 
 if CONFIG["CC_TYPE"] in ("clang", "gcc"):
     CXXFLAGS += ["-Wno-error=shadow"]
-
-REQUIRES_UNIFIED_BUILD = True

layout/generic/nsIFrame.cpp

@@ -17,6 +17,7 @@
 #include "mozilla/ComputedStyle.h"
 #include "mozilla/DebugOnly.h"
 #include "mozilla/DisplayPortUtils.h"
+#include "mozilla/dom/DocumentInlines.h"
 #include "mozilla/dom/AncestorIterator.h"
 #include "mozilla/dom/ElementInlines.h"
 #include "mozilla/dom/ImageTracker.h"

layout/generic/nsImageFrame.cpp

@@ -37,6 +37,7 @@
 
 #include "nsCOMPtr.h"
 #include "nsFontMetrics.h"
+#include "nsIFrameInlines.h"
 #include "nsIImageLoadingContent.h"
 #include "nsImageLoadingContent.h"
 #include "nsImageRenderer.h"