Fix flake in EngagementTimeUtilTest

timeSinceLastEngagement_shouldReportElapsedTimeBetweenTimestamps gets
the current time twice. If the system time ticks over between calls it
will register 1 ms more than the test expects.

R=yusufo@chromium.org

Bug: 947572
Change-Id: Ic5b1bcda2300e217b66567ba54a9ccaa5e515374
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1708844
Auto-Submit: Joe Mason <joenotcharles@google.com>
Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Commit-Queue: Joe Mason <joenotcharles@google.com>
Cr-Commit-Position: refs/heads/master@{#680002}

chrome/android/junit/src/org/chromium/chrome/browser/tasks/EngagementTimeUtilTest.java

@@ -42,9 +42,10 @@ public final class EngagementTimeUtilTest {
 
     @Test
     public void timeSinceLastEngagement_shouldReportElapsedTimeBetweenTimestamps() {
+        long currentTimeMillis = System.currentTimeMillis();
         assertEquals(TEST_ELAPSED_MS,
                 mEngagementTimeUtil.timeSinceLastEngagement(
-                        System.currentTimeMillis() - (2L * TEST_ELAPSED_MS),
-                        System.currentTimeMillis() - TEST_ELAPSED_MS));
+                        currentTimeMillis - (2L * TEST_ELAPSED_MS),
+                        currentTimeMillis - TEST_ELAPSED_MS));
     }
 }