GestureNav: Use Assert.assert* instead of assert

Replaces |assert| which can be removed in release build
with one of Assert.assert* variations in test.

Bug: 1131424
Change-Id: Iadba51d09fb857a2db0f41357690361885e3c6fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2437669Reviewed-by: Donn Denman <donnd@chromium.org>
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814011}

chrome/android/javatests/src/org/chromium/chrome/browser/gesturenav/NavigationHandlerTest.java

@@ -250,7 +250,7 @@ public class NavigationHandlerTest {
         // |triggerUi| can be invoked by SwipeRefreshHandler on the rendered
         // page. Make sure this won't crash after the coordinator (and also
         // handler action delegate) is destroyed.
-        assert !mNavigationHandler.triggerUi(LEFT_EDGE, 0, 0);
+        Assert.assertFalse(mNavigationHandler.triggerUi(LEFT_EDGE, 0, 0));
 
         // Just check we're still on the same URL.
         Assert.assertEquals(mTestServer.getURL(RENDERED_PAGE),