Make marquee-scroll a pixel test to avoid flakyness in render tree output.

LayoutTests/platform/win/fast/html/marquee-scroll-expected.txt

Index: LayoutTests/platform/win/fast/html/marquee-scroll-expected.txt
diff --git a/LayoutTests/platform/win/fast/html/marquee-scroll-expected.txt b/LayoutTests/platform/win/fast/html/marquee-scroll-expected.txt
deleted file mode 100644
index 582f2e6b62a6210c2306067628558f671a4fc821..0000000000000000000000000000000000000000
--- a/LayoutTests/platform/win/fast/html/marquee-scroll-expected.txt
+++ /dev/null
@@ -1,31 +0,0 @@
-layer at (0,0) size 800x600
-  LayoutView at (0,0) size 800x600
-layer at (0,0) size 800x600
-  LayoutBlockFlow {HTML} at (0,0) size 800x600
-    LayoutBlockFlow {BODY} at (8,8) size 784x584
-      LayoutBlockFlow {P} at (0,0) size 784x18
-        LayoutText {#text} at (0,0) size 55x17
-          text run at (0,0) width 55: "Test for "
-        LayoutInline {A} at (0,0) size 69x17 [color=#0000EE]
-          LayoutText {#text} at (54,0) size 69x17
-            text run at (54,0) width 69: "bug 15263"
-        LayoutText {#text} at (122,0) size 399x17
-          text run at (122,0) width 399: ": REGRESSION: scrolldelay=0 causes marquee not to display"
-      LayoutBlockFlow {P} at (0,34) size 784x36
-        LayoutText {#text} at (0,0) size 747x35
-          text run at (0,0) width 747: "The marquee below is defined with a scrollDelay value of zero and with the truespeed attribute assigned to an empty"
-          text run at (0,18) width 45: "string. "
-          text run at (44,18) width 573: "It should scroll until the text, \"The marquee scroll test passed\" is visible and left justified."
-      LayoutBlockFlow {P} at (0,86) size 784x36
-        LayoutText {#text} at (0,0) size 774x35
-          text run at (0,0) width 774: "This test uses cyan characters to make the result image deterministic. (Otherwise, the result image changes depending on"
-          text run at (0,18) width 652: "when the content_shell takes a snapshot.) In order to run this test manually, change the color to black."
-      LayoutBlockFlow (anonymous) at (0,138) size 784x18
-        LayoutText {#text} at (0,0) size 0x0
-layer at (8,146) size 392x18
-  LayoutBlockFlow {MARQUEE} at (0,0) size 392x18 [bgcolor=#00FFFF]
-    LayoutBlockFlow {DIV} at (0,0) size 392x18
-      LayoutInline {SPAN} at (0,0) size 197x17 [color=#00FFFF]
-        LayoutText {#text} at (0,0) size 197x17
-          text run at (0,0) width 197: "The marquee scroll test passed"
-      LayoutText {#text} at (0,0) size 0x0