Fix test crashes related to AccountManagerHelper.

chrome/android/javatests/src/org/chromium/chrome/browser/precache/PrecacheUMATest.java

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.precache;
 
+import android.support.test.InstrumentationRegistry;
 import android.support.test.filters.SmallTest;
 
+import org.junit.After;
 import org.junit.Assert;
+import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
 import org.chromium.base.ContextUtils;
 import org.chromium.base.library_loader.LibraryLoader;
 import org.chromium.base.test.BaseJUnit4ClassRunner;
 import org.chromium.base.test.util.Feature;
 import org.chromium.base.test.util.MetricsUtils.HistogramDelta;
 import org.chromium.base.test.util.RetryOnFailure;
+import org.chromium.chrome.test.util.browser.signin.SigninTestUtil;
 import org.chromium.content.browser.test.NativeLibraryTestRule;
 
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
 /**
  * Tests of {@link PrecacheUMA}.
  */
 @RunWith(BaseJUnit4ClassRunner.class)
 public class PrecacheUMATest {
     @Rule
     public NativeLibraryTestRule mActivityTestRule = new NativeLibraryTestRule();
 
+    @Before
+    public void setUp() {
+        // TODO (thildebr): This is just copied from the ChromeBrowserTestRule because we need to
+        // be selective of when we load the native library, so we can't just use the rule.
+        SigninTestUtil.setUpAuthForTest(InstrumentationRegistry.getInstrumentation());
+    }
+
+    @After
+    public void tearDown() {
+        // TODO (thildebr): Also copied from ChromeBrowserTestRule until there's a better way.
+        SigninTestUtil.resetSigninState();
+        SigninTestUtil.tearDownAuthForTest();
+    }
+
     @Test
     @SmallTest
     @Feature({"Precache"})
     public void testUMAEventBitPositionAndMask() {
         // Test the bitmask and bit position of all UMA Events.
         for (int event = PrecacheUMA.Event.EVENT_START; event < PrecacheUMA.Event.EVENT_END;
                 ++event) {
             long bitmask = PrecacheUMA.Event.getBitMask(event);
             Assert.assertTrue(bitmask > 0);
             Assert.assertEquals(bitmask, 1L << PrecacheUMA.Event.getBitPosition(event));
@@ skipping 100 matching lines @@
             if (events.contains(event)) {
                 Assert.assertEquals(
                         1, histograms[PrecacheUMA.Event.getBitPosition(event)].getDelta());
             } else {
                 Assert.assertEquals(
                         0, histograms[PrecacheUMA.Event.getBitPosition(event)].getDelta());
             }
         }
     }
 }