Add findbugs filter to exclude UiThreadTestRule in java tests

build/android/findbugs_filter/findbugs_exclude.xml

Index: build/android/findbugs_filter/findbugs_exclude.xml
diff --git a/build/android/findbugs_filter/findbugs_exclude.xml b/build/android/findbugs_filter/findbugs_exclude.xml
index f6a1394f2df8b548489277c37281b519fc71e30c..3f0316c32e54c605424112044938b42445d2f1a8 100644
--- a/build/android/findbugs_filter/findbugs_exclude.xml
+++ b/build/android/findbugs_filter/findbugs_exclude.xml
@@ -26,4 +26,12 @@ In particular, ~ at the start of a string means it's a regex.
   https://developer.android.com/reference/java/security/AccessController.html
   -->
   <Bug pattern="DP_CREATE_CLASSLOADER_INSIDE_DO_PRIVILEGED" />
+
+  <!-- Ignore unused public Rule in instrumentation tests -->
+  <Match>
+    <Class name="~.*\.*Test" />
+    <Field type="android.support.test.rule.UiThreadTestRule" />
+    <Bug pattern="URF_UNREAD_PUBLIC_OR_PROTECTED_FIELD" />

[jbudorick, 2017/03/22 15:43:48]

Is UiThreadTestRule typically public or protected rather than private? Why?

[jbudorick, 2017/03/22 15:48:07]

ah, nvm, found http://junit.org/junit4/javadoc/4.12/org/junit/Rule.html

[the real yoland, 2017/03/22 15:50:52]

It's always public because junit4 requires @Rule field to be public (in case
security manager blocks class from accessing private field reflectively)

+  </Match>
+
 </FindBugsFilter>