Fix tests broken by default text color change.

sky/tests/lowlevel/iframe-expected.txt

Index: sky/tests/lowlevel/iframe-expected.txt
diff --git a/sky/tests/lowlevel/iframe-expected.txt b/sky/tests/lowlevel/iframe-expected.txt
deleted file mode 100644
index 0bf0008e298e066ffe839ddc581d0aab5b44c098..0000000000000000000000000000000000000000
--- a/sky/tests/lowlevel/iframe-expected.txt
+++ /dev/null
@@ -1,21 +0,0 @@
-layer at (0,0) size 800x600
-  RenderView {#document} at (0,0) size 800x600
-    RenderFlexibleBox {sky} at (0,0) size 800x438
-      RenderParagraph {p} at (0,0) size 800x194
-        RenderText {#text} at (0,175) size 81x19
-          text run at (0,175) width 81: "This is an "
-        RenderText {#text} at (420,175) size 77x19
-          text run at (420,175) width 77: " element."
-      RenderParagraph {p} at (0,194) size 800x200
-        RenderText {#text} at (0,0) size 99x19
-          text run at (0,0) width 99: "Placeholder."
-      RenderParagraph {p} at (0,394) size 800x44
-        RenderText {#text} at (0,25) size 223x19
-          text run at (0,25) width 223: "Small iframe should render "
-        RenderText {#text} at (522,25) size 82x19
-          text run at (522,25) width 82: " correctly."
-layer at (81,0) size 340x190
-  RenderReplaced {iframe} at (80.67,0) size 340x190 [border: (20px solid #000000)]
-layer at (223,394) size 300x40
-  RenderReplaced {iframe} at (222.81,0) size 300x40
-