Revert of Clip scrollbars to box bounds when they don't fit.

third_party/WebKit/LayoutTests/platform/linux/compositing/overflow/selection-gaps-toggling-expected.txt

 This test passes if the container's scrolling contents layer (the first child of the GraphicsLayer with 4 children) doesn't draw content at all, and its scrolling block selection layer (the child of the scrolling contents layer) draws content only on iteration 2. The scrolling block selection layer should also be much smaller than the scrolling contents layer.
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@@ skipping 18 matching lines @@
             {
               "bounds": [285, 485],
               "children": [
                 {
                   "bounds": [285, 665],
                   "shouldFlattenTransform": false
                 }
               ]
             },
             {
-              "bounds": [300, 500],
               "children": [
                 {
                   "position": [0, 485],
                   "bounds": [285, 15]
                 },
                 {
                   "position": [285, 0],
                   "bounds": [15, 485]
                 },
                 {
@@ skipping 77 matching lines @@
         }
       ]
     }
   ]
 }
 
 
 *** iteration 2: ***
 
 {
-  "bounds": [785, 2514],
+  "bounds": [785, 2498],
   "children": [
     {
-      "bounds": [785, 2514],
+      "bounds": [785, 2498],
       "contentsOpaque": true,
       "drawsContent": true,
       "children": [
         {
           "position": [8, 68],
           "bounds": [300, 500],
           "drawsContent": true,
           "children": [
             {
               "bounds": [285, 485],
               "children": [
                 {
                   "bounds": [285, 665],
                   "shouldFlattenTransform": false
                 }
               ]
             },
             {
-              "bounds": [300, 500],
               "children": [
                 {
                   "position": [0, 485],
                   "bounds": [285, 15]
                 },
                 {
                   "position": [285, 0],
                   "bounds": [15, 485]
                 },
                 {
@@ skipping 77 matching lines @@
         }
       ]
     }
   ]
 }
 
 
 *** iteration 3: ***
 
 {
-  "bounds": [785, 4434],
+  "bounds": [785, 4402],
   "children": [
     {
-      "bounds": [785, 4434],
+      "bounds": [785, 4402],
       "contentsOpaque": true,
       "drawsContent": true,
       "children": [
         {
           "position": [8, 68],
           "bounds": [300, 500],
           "drawsContent": true,
           "children": [
             {
               "bounds": [285, 485],
               "children": [
                 {
                   "bounds": [285, 665],
                   "shouldFlattenTransform": false
                 }
               ]
             },
             {
-              "bounds": [300, 500],
               "children": [
                 {
                   "position": [0, 485],
                   "bounds": [285, 15]
                 },
                 {
                   "position": [285, 0],
                   "bounds": [15, 485]
                 },
                 {
@@ skipping 73 matching lines @@
           "bounds": [100, 50],
           "contentsOpaque": true,
           "drawsContent": true,
           "backgroundColor": "#FFA500"
         }
       ]
     }
   ]
 }