DO NOT MERGE Add UiAutomationTest#testWindowContentFrameStats to knownfailures

The test is not able to pass in a reliable manner without the patch
75b55d0846159543aafc1b7420915497fce9b3f1 which is only available
in Android 5.1 (Lollipop MR1)

Bug: 18039218
Change-Id: I50ba892f893b32243b8026d1ec9f1aaa6a7bda92
diff --git a/tests/expectations/knownfailures.txt b/tests/expectations/knownfailures.txt
index 48e5194..3abb1f7 100644
--- a/tests/expectations/knownfailures.txt
+++ b/tests/expectations/knownfailures.txt
@@ -1,5 +1,12 @@
 [
 {
+  description: "testWindowContentFrameStats is flaky without 75b55d0846159543aafc1b7420915497fce9b3f1",
+  names: [
+    "android.app.uiautomation.cts.UiAutomationTest#testWindowContentFrameStats"
+  ],
+  bug: 18039218
+},
+{
   description: "the UsageStats is not yet stable enough",
   names: [
     "android.app.usage.cts.UsageStatsTest"