Fix several corner case issues of scrollbar paint invalidation

third_party/WebKit/LayoutTests/fast/repaint/overflow-scroll-body-appear-expected.txt

Index: third_party/WebKit/LayoutTests/fast/repaint/overflow-scroll-body-appear-expected.txt
diff --git a/third_party/WebKit/LayoutTests/fast/repaint/overflow-scroll-body-appear-expected.txt b/third_party/WebKit/LayoutTests/fast/repaint/overflow-scroll-body-appear-expected.txt
index d62068de4f2a79cc4bb0aa81f77aee0a40348834..14b7c55f6ffb2418509929e06ff56272ef5e6db9 100644
--- a/third_party/WebKit/LayoutTests/fast/repaint/overflow-scroll-body-appear-expected.txt
+++ b/third_party/WebKit/LayoutTests/fast/repaint/overflow-scroll-body-appear-expected.txt
@@ -1,18 +1,20 @@
 {
-  "bounds": [2008, 2092],
+  "bounds": [2008, 2096],
   "children": [
     {
-      "bounds": [2008, 2092],
+      "bounds": [2008, 2096],
       "contentsOpaque": true,
       "drawsContent": true,
       "repaintRects": [
         [785, 585, 15, 15],
-        [8, 50, 784, 18],
-        [8, 50, 769, 18],
-        [8, 16, 2000, 2068],
-        [8, 16, 784, 18],
-        [8, 16, 769, 18],
-        [0, 0, 2008, 2092],
+        [785, 0, 15, 585],
+        [8, 52, 784, 20],
+        [8, 52, 769, 20],
+        [8, 16, 2000, 2072],
+        [8, 16, 784, 20],
+        [8, 16, 769, 20],
+        [0, 585, 785, 15],
+        [0, 0, 2008, 2096],
         [0, 0, 785, 585]
       ],
       "paintInvalidationClients": [
@@ -27,8 +29,7 @@
         "LayoutBlockFlow BODY",
         "LayoutBlockFlow P",
         "LayoutBlockFlow P",
-        "HorizontalScrollbar",
-        "VerticalScrollbar"
+        "LayoutView #document"
       ]
     }
   ]