[Multicolumn] Avoid floating point when calculating the actual column…

… count

https://bugs.webkit.org/show_bug.cgi?id=257030

Reviewed by Alan Baradlay.

Merge: https://chromium.googlesource.com/chromium/src.git/+/4a931c534e4b27b809b67d0207c7dc0d8a28faf0

This patch get rid of 'floating point' calculation for column count,
which can be error-prone.

The test is already imported:
imported/blink/fast/pagination/short-pages-tall-content.html

* Source/WebCore/rendering/RenderMultiColumnSet.cpp:
(RenderMultiColumnSet::columnCount):

Canonical link: https://commits.webkit.org/264667@main

Source/WebCore/rendering/RenderMultiColumnSet.cpp

@@ -456,7 +456,10 @@ unsigned RenderMultiColumnSet::columnCount() const
     if (logicalHeightInColumns <= 0)
         return 1;
 
-    unsigned count = ceilf(static_cast<float>(logicalHeightInColumns) / computedColumnHeight);
+    unsigned count = (logicalHeightInColumns / computedColumnHeight).floor();
+    // logicalHeightInColumns may be saturated, so detect the remainder manually.
+    if (count * computedColumnHeight < logicalHeightInColumns)
+        ++count;
     ASSERT(count >= 1);
     return count;
 }