Fix problems with flakes in SVG LayoutTests.

Source/core/rendering/svg/SVGRenderTreeAsText.cpp

Index: Source/core/rendering/svg/SVGRenderTreeAsText.cpp
diff --git a/Source/core/rendering/svg/SVGRenderTreeAsText.cpp b/Source/core/rendering/svg/SVGRenderTreeAsText.cpp
index 4de4347697837e04be12955a48a5d7dfc22ba71b..01104f273a4a743399b48c2a18bddf8cf8012925 100644
--- a/Source/core/rendering/svg/SVGRenderTreeAsText.cpp
+++ b/Source/core/rendering/svg/SVGRenderTreeAsText.cpp
@@ -327,9 +327,35 @@ static void writeStyle(TextStream& ts, const RenderObject& object)
     writeIfNotEmpty(ts, "end marker", svgStyle.markerEndResource());
 }
 
+static float snapToCloseInteger(float value)
+{
+    // Due to floating point arithmetic uncertainties we may sometimes end up at
+    // something like 4.99999952 when pure arithmetic would have given 5.
+    // To give predictable results in debug ouput, snap numbers very close to
+    // integers to integers. This matters because sometimes numbers are truncated
+    // rather than rounded before being viewed as integers.
+    const double epsilon = 0.00001;
+    if (fabs(value - round(value)) < epsilon)
+        return static_cast<float>(round(value));
+    return value;
+}
+
+static FloatPoint snapToCloseInteger(FloatPoint point)
+{
+    return FloatPoint(snapToCloseInteger(point.x()), snapToCloseInteger(point.y()));
+}
+
+static FloatRect snapToCloseInteger(FloatRect rect)
+{
+    FloatPoint bottomRight = snapToCloseInteger(rect.maxXMaxYCorner());
+    FloatPoint topLeft = snapToCloseInteger(rect.minXMinYCorner());
+    return FloatRect(topLeft, bottomRight - topLeft);
+}
+
 static TextStream& writePositionAndStyle(TextStream& ts, const RenderObject& object)
 {
-    ts << " " << enclosingIntRect(const_cast<RenderObject&>(object).absoluteClippedOverflowRect());
+    FloatRect rect = snapToCloseInteger(object.absoluteClippedOverflowRect());

[Daniel Bratell, 2015/01/22 09:21:40]

This is too late. It's in the conversion from float to LayoutRect the large
error is introduced.

+    ts << " " << enclosingIntRect(rect);
     writeStyle(ts, object);
     return ts;
 }