Moving clock timeout flakiness guard in test to 20 ms

LayoutTests/fast/mediastream/RTCPeerConnection-stats.html

Index: LayoutTests/fast/mediastream/RTCPeerConnection-stats.html
diff --git a/LayoutTests/fast/mediastream/RTCPeerConnection-stats.html b/LayoutTests/fast/mediastream/RTCPeerConnection-stats.html
index 6f35b9101c674c1e0b8843e2021e323b42174a5b..89945325fff158eb774ddb7e05d6a5371c01961b 100644
--- a/LayoutTests/fast/mediastream/RTCPeerConnection-stats.html
+++ b/LayoutTests/fast/mediastream/RTCPeerConnection-stats.html
@@ -56,8 +56,9 @@ function statsHandler2(status)
     timestamp = local.timestamp;
     // Windows XP sometimes gives time that appears to go backwards.
     // This hack will make the tests non-flaky if it never goes backwards
-    // by more than 1 millisecond.
-    fudgeForXP = 1;
+    // by more than 20 milliseconds.
+    // Up to 10 milliseconds has been observed on XP, 2 milliseconds on Win7.
+    fudgeForXP = 20;
     timediff = timestamp - startTime + fudgeForXP;
     shouldBeGreaterThanOrEqual('timediff', '0');
     shouldBeGreaterThanOrEqual('local.names().length', '1');