Tune performance test parameters.

LayoutTests/http/tests/perf/large-inlined-script.html

Index: LayoutTests/http/tests/perf/large-inlined-script.html
diff --git a/LayoutTests/http/tests/perf/large-inlined-script.html b/LayoutTests/http/tests/perf/large-inlined-script.html
index 360512cbc2ad921c8b5beef0e28d467c74a68eb7..794a68ce60d79425de20d5cbd7b8e41876ab537e 100644
--- a/LayoutTests/http/tests/perf/large-inlined-script.html
+++ b/LayoutTests/http/tests/perf/large-inlined-script.html
@@ -20,9 +20,10 @@ function test(magnitude, callback)
 Magnitude.description("This tests time complexity of parsing HTML with large inlined script.");
 Magnitude.initialExponent = 15;
 Magnitude.numPoints = 4;
-Magnitude.tolerance = 0.25;
-Magnitude.numTrials = 5;
-Magnitude.successThreshold = 0.4; // 2 out of 5
+Magnitude.trim = 1;
+Magnitude.tolerance = 0.2;
+Magnitude.numTrials = 4;
+Magnitude.successThreshold = 0.5; // 2 out of 4
 Magnitude.runAsync(setupFunction, test, Magnitude.LINEAR);
 </script>
 </head>