REGRESSION(r160441): 2 layout test failures on GTK after enabling saturated layout arithmetic

[Zan Dobersek]

r160441 enabled the saturated layout arithmetic, but caused the following two tests to fail:
 fast/block/float/overhanging-tall-block.html
 scrollbars/scrollbar-large-overflow-rectangle.html

Diff for fast/block/float/overhanging-tall-block.html (and the new pixel output also seems incorrect):
--- /home/slave/webkitgtk/gtk-linux-64-release/build/layout-test-results/fast/block/float/overhanging-tall-block-expected.txt
+++ /home/slave/webkitgtk/gtk-linux-64-release/build/layout-test-results/fast/block/float/overhanging-tall-block-actual.txt
@@ -1,11 +1,11 @@
-layer at (0,0) size 800x22278428
+layer at (0,0) size 800x33554431
   RenderView at (0,0) size 800x600
-layer at (0,0) size 800x22278428 backgroundClip at (0,0) size 800x16777216 clip at (0,0) size 800x16777216 outlineClip at (0,0) size 800x16777216
-  RenderBlock {HTML} at (0,0) size 800x22278428
-    RenderBody {BODY} at (8,8) size 784x22278412
-      RenderBlock {DIV} at (0,0) size 784x22278410
-      RenderBlock {DIV} at (0,22278412) size 784x0
-      RenderBlock {DIV} at (0,22278414) size 784x0
-layer at (10,10) size 201x22278406 backgroundClip at (10,10) size 201x16777206 clip at (11,11) size 199x16777205 outlineClip at (0,0) size 800x16777216
-  RenderTextControl {TEXTAREA} at (2,2) size 201x22278406 [bgcolor=#FFFFFF] [border: (1px solid #000000)]
+layer at (0,0) size 800x33554431 backgroundClip at (0,0) size 800x16777216 clip at (0,0) size 800x16777216 outlineClip at (0,0) size 800x16777216
+  RenderBlock {HTML} at (0,0) size 800x33554431
+    RenderBody {BODY} at (8,8) size 784x33554423
+      RenderBlock {DIV} at (0,0) size 784x33554431
+      RenderBlock {DIV} at (0,33554431) size 784x0
+      RenderBlock {DIV} at (0,33554431) size 784x0
+layer at (10,11) size 201x33554431 backgroundClip at (10,11) size 201x16777205 clip at (11,12) size 199x16777204 outlineClip at (0,0) size 800x16777216
+  RenderTextControl {TEXTAREA} at (2,3) size 201x33554428 [bgcolor=#FFFFFF] [border: (1px solid #000000)]
     RenderBlock {DIV} at (3,3) size 195x17

Diff for scrollbars/scrollbar-large-overflow-rectangle.html:
--- /home/slave/webkitgtk/gtk-linux-64-release/build/layout-test-results/scrollbars/scrollbar-large-overflow-rectangle-expected.txt
+++ /home/slave/webkitgtk/gtk-linux-64-release/build/layout-test-results/scrollbars/scrollbar-large-overflow-rectangle-actual.txt
@@ -1,3 +1,3 @@
 This page should be scrollable
-PASS
+FAIL document.body.scrollHeight = 600
 

http://trac.webkit.org/changeset/160441
http://webkit-test-results.appspot.com/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=fast%2Fblock%2Ffloat%2Foverhanging-tall-block.html%2Cscrollbars%2Fscrollbar-large-overflow-rectangle.html

[Sergio Villar Senin]

Unskipped in https://trac.webkit.org/changeset/166875 as it was working