Fix TracingSettingsTest.testRecordTrace issue on newer AndroidX versions

testRecordTrace calls Preference#performClick to simulate a button
click, which doesn't work on newer versions of the AndroidX preference
library because clicks are ignored if the preference isn't selectable.
This particular method also deosn't appear to be part of the public API.
This CL replaces the performClick call with a call to the Preference's
OnPreferenceClickListener, which correctly simulates a button click.

Bug: 1092986
Change-Id: I1be5c20c9ee020dce63f584dab754642593ddf45
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2240397Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Robbie McElrath <rmcelrath@chromium.org>
Cr-Commit-Position: refs/heads/master@{#777224}

chrome/android/javatests/src/org/chromium/chrome/browser/tracing/settings/TracingSettingsTest.java

@@ -167,7 +167,7 @@ public class TracingSettingsTest {
             Assert.assertEquals(TracingSettings.MSG_START, startTracingButton.getTitle());
 
             // Tap the button to start recording a trace.
-            startTracingButton.performClick();
+            startTracingButton.getOnPreferenceClickListener().onPreferenceClick(startTracingButton);
 
             Assert.assertEquals(
                     TracingController.State.STARTING, TracingController.getInstance().getState());