Keep effectiveZoom finite

Source/core/style/ComputedStyle.h

Index: Source/core/style/ComputedStyle.h
diff --git a/Source/core/style/ComputedStyle.h b/Source/core/style/ComputedStyle.h
index 84bca97d0b11b3746168b62dba3e15167982b0ef..1d10aa907987743c9afe107c7e84ddf0e656cd5c 100644
--- a/Source/core/style/ComputedStyle.h
+++ b/Source/core/style/ComputedStyle.h
@@ -1887,9 +1887,10 @@ inline bool ComputedStyle::setZoom(float f)
 
 inline bool ComputedStyle::setEffectiveZoom(float f)
 {
-    if (compareEqual(rareInheritedData->m_effectiveZoom, f))
+    float clampedEffectiveZoom = clampTo<float>(f);

[fs, 2015/06/23 21:11:57]

In practice this is just a "gratuitous max value" - a fairly large one at that.
Could (should?) quite possibly be a smaller value. With this value, it still
fairly trivial to overflow to Infinity (multiplication with anything > 1 will do
it for instance). It works better than the actual Infinity though, because a
quite common operation/case is "0 * Infinity => NaN" (value == 0, zoom ==
Infinity), which now becomes "0 * max() => 0". Will change to smaller value for
no fee at all.

+    if (compareEqual(rareInheritedData->m_effectiveZoom, clampedEffectiveZoom))
         return false;
-    rareInheritedData.access()->m_effectiveZoom = f;
+    rareInheritedData.access()->m_effectiveZoom = clampedEffectiveZoom;
     return true;
 }