Remove frame flattening support as Chromium has no intention of using it

LayoutTests/fast/frames/flattening/frameset-flattening-subframesets-expected.txt

Index: LayoutTests/fast/frames/flattening/frameset-flattening-subframesets-expected.txt
diff --git a/LayoutTests/fast/frames/flattening/frameset-flattening-subframesets-expected.txt b/LayoutTests/fast/frames/flattening/frameset-flattening-subframesets-expected.txt
deleted file mode 100644
index a951fbfec9012d4317bbb3541729a107d4421b16..0000000000000000000000000000000000000000
--- a/LayoutTests/fast/frames/flattening/frameset-flattening-subframesets-expected.txt
+++ /dev/null
@@ -1,58 +0,0 @@
-layer at (0,0) size 900x630
-  RenderView at (0,0) size 785x585
-layer at (0,0) size 785x630
-  RenderBlock {HTML} at (0,0) size 785x630
-    RenderFrameSet {FRAMESET} at (0,0) size 900x630
-      RenderFrameSet {FRAMESET} at (0,0) size 900x150
-        RenderFrame {FRAME} at (0,0) size 450x150
-          layer at (0,0) size 450x150
-            RenderView at (0,0) size 450x150
-          layer at (0,0) size 450x150
-            RenderBlock {HTML} at (0,0) size 450x150
-              RenderBody {BODY} at (8,8) size 434x126 [bgcolor=#008000]
-                RenderBlock {P} at (0,0) size 434x18
-                  RenderText {#text} at (0,0) size 364x18
-                    text run at (0,0) width 364: "A frameset flattening test that only works inside the DRT."
-                RenderBlock {P} at (0,34) size 434x36
-                  RenderText {#text} at (0,0) size 414x36
-                    text run at (0,0) width 414: "This frame is inside frameset 1 and should be at least 450px wide,"
-                    text run at (0,18) width 201: "150px tall and not be scrollable."
-          layer at (0,0) size 450x50
-            RenderBlock (positioned) {DIV} at (0,0) size 450x50
-        RenderFrame {FRAME} at (450,0) size 450x150
-          layer at (0,0) size 450x150
-            RenderView at (0,0) size 450x150
-          layer at (0,0) size 450x150
-            RenderBlock {HTML} at (0,0) size 450x150
-              RenderBody {BODY} at (8,8) size 434x126 [bgcolor=#FF0000]
-                RenderBlock {P} at (0,0) size 434x36
-                  RenderText {#text} at (0,0) size 414x36
-                    text run at (0,0) width 414: "This frame is inside frameset 1 and should be at least 450px wide,"
-                    text run at (0,18) width 201: "150px tall and not be scrollable."
-          layer at (0,0) size 450x150
-            RenderBlock (positioned) {DIV} at (0,0) size 450x150
-      RenderFrameSet {FRAMESET} at (0,150) size 900x480
-        RenderFrame {FRAME} at (0,0) size 450x480
-          layer at (0,0) size 450x480
-            RenderView at (0,0) size 450x480
-          layer at (0,0) size 450x480
-            RenderBlock {HTML} at (0,0) size 450x480
-              RenderBody {BODY} at (8,8) size 434x456 [bgcolor=#FFFF00]
-                RenderBlock {P} at (0,0) size 434x36
-                  RenderText {#text} at (0,0) size 414x36
-                    text run at (0,0) width 414: "This frame is inside frameset 2 and should be at least 450px wide,"
-                    text run at (0,18) width 201: "400px tall and not be scrollable."
-          layer at (0,0) size 200x450
-            RenderBlock (positioned) {DIV} at (0,0) size 200x450
-        RenderFrame {FRAME} at (450,0) size 450x480
-          layer at (0,0) size 450x480
-            RenderView at (0,0) size 450x480
-          layer at (0,0) size 450x480
-            RenderBlock {HTML} at (0,0) size 450x480
-              RenderBody {BODY} at (8,8) size 434x456 [bgcolor=#0000FF]
-                RenderBlock {P} at (0,0) size 434x36
-                  RenderText {#text} at (0,0) size 414x36
-                    text run at (0,0) width 414: "This frame is inside frameset 2 and should be at least 450px wide,"
-                    text run at (0,18) width 201: "400px tall and not be scrollable."
-          layer at (0,0) size 450x450
-            RenderBlock (positioned) {DIV} at (0,0) size 450x450