Button elements are clipping overflow by default

LayoutTests/platform/linux/fast/forms/control-clip-overflow-expected.txt

Index: LayoutTests/platform/linux/fast/forms/control-clip-overflow-expected.txt
diff --git a/LayoutTests/platform/linux/fast/forms/control-clip-overflow-expected.txt b/LayoutTests/platform/linux/fast/forms/control-clip-overflow-expected.txt
index 809f3d3694cfc129a30ef8614f15c81bf5f88c4e..d8c21045c63b339f59cae91f9334353d0e53bd6d 100644
--- a/LayoutTests/platform/linux/fast/forms/control-clip-overflow-expected.txt
+++ b/LayoutTests/platform/linux/fast/forms/control-clip-overflow-expected.txt
@@ -17,8 +17,9 @@ layer at (0,0) size 800x600
         LayoutText {#text} at (230,20) size 4x19
           text run at (230,20) width 4: "."
       LayoutBlockFlow {P} at (0,56) size 784x20
-        LayoutText {#text} at (0,0) size 386x19
-          text run at (0,0) width 386: "There should not be scroll bars below the popup and the button."
+        LayoutText {#text} at (0,0) size 722x19
+          text run at (0,0) width 300: "There should not be scroll bars below the popup. "
+          text run at (300,0) width 422: "There should be scrollbars below the button (see crbug.com/465429)."
 layer at (8,100) size 100x50
   LayoutBlockFlow {DIV} at (0,92) size 100x50
     LayoutMenuList {SELECT} at (0,0) size 80x20 [bgcolor=#C0C0C0] [border: (1px solid #A9A9A9)]
@@ -26,7 +27,7 @@ layer at (8,100) size 100x50
         LayoutText at (4,1) size 158x16
           text run at (4,1) width 158: "Lorem ipsum dolor sit amet"
     LayoutText {#text} at (0,0) size 0x0
-layer at (8,170) size 100x50
+layer at (8,170) size 100x50 clip at (8,170) size 100x35 scrollWidth 166
   LayoutBlockFlow {DIV} at (0,162) size 100x50
     LayoutButton {BUTTON} at (0,0) size 80x22 [bgcolor=#C0C0C0] [border: (2px outset #C0C0C0)]
       LayoutBlockFlow (anonymous) at (8,3) size 64x16