Add CTS test for Roboto fonts

As of L, the CDD now requires Roboto fonts for fidelity to the Material
Design theme. The Roboto 2 font also has significantly expanded Unicode
coverage including many characters from Unicode 7. This test verifies
the presence and appearance of the fonts, and also coverage, using
golden reference images. The threshold is tuned to allow for legitimate
variations in rendering.

Bug: 17109280
Change-Id: I7abbed6cad2ecbb98caa8da2f0f8c8d51a419a91
diff --git a/tests/expectations/knownfailures.txt b/tests/expectations/knownfailures.txt
index 9ae041c..ae78695 100644
--- a/tests/expectations/knownfailures.txt
+++ b/tests/expectations/knownfailures.txt
@@ -357,5 +357,12 @@
     "android.media.cts.ImageReaderDecoderTest#testHwAVCDecode360pForFlexibleYuv"
   ],
   bug: 17144778
+},
+{
+  description: "Roboto font tests are not yet known good on all devices",
+  names: [
+    "android.uirendering.cts.testclasses.FontRenderingTests"
+  ],
+  bug: 17109280
 }
 ]