Fix duration check in base_unittest's TimeTicks.ThreadNow.

This test is flaky in CrOS VMs:
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/chromeos-amd64-generic-rel/14479
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/chromeos-amd64-generic-rel/14493

Flakiness dashboard is quite black:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=base_unittests&tests=ThreadTicks.ThreadNow

Bug: 352633, 840967
Change-Id: Ia6efb4070bcef525992015f766599846a13ee1ec
Reviewed-on: https://chromium-review.googlesource.com/1101412Reviewed-by: Gabriel Charette <gab@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567392}

base/time/time_unittest.cc

@@ -989,14 +989,7 @@ TEST(ThreadTicks, MAYBE_NowOverride) {
   EXPECT_GT(ThreadTicks::Max(), subtle::ThreadTicksNowIgnoringOverride());
 }
 
-// Fails frequently on Android http://crbug.com/352633 with:
-// Expected: (delta_thread.InMicroseconds()) > (0), actual: 0 vs 0
-#if defined(OS_ANDROID)
-#define MAYBE_ThreadNow DISABLED_ThreadNow
-#else
-#define MAYBE_ThreadNow ThreadNow
-#endif
-TEST(ThreadTicks, MAYBE_ThreadNow) {
+TEST(ThreadTicks, ThreadNow) {
   if (ThreadTicks::IsSupported()) {
     ThreadTicks::WaitUntilInitialized();
     TimeTicks begin = TimeTicks::Now();
@@ -1010,7 +1003,7 @@ TEST(ThreadTicks, MAYBE_ThreadNow) {
     TimeDelta delta = end - begin;
     TimeDelta delta_thread = end_thread - begin_thread;
     // Make sure that some thread time have elapsed.
-    EXPECT_GT(delta_thread.InMicroseconds(), 0);
+    EXPECT_GE(delta_thread.InMicroseconds(), 0);
     // But the thread time is at least 9ms less than clock time.
     TimeDelta difference = delta - delta_thread;
     EXPECT_GE(difference.InMicroseconds(), 9000);