Reland "Add MainSettingsFragmentTest"

This reverts commit 2a103d18.

Reason for revert: Will fix the flakiness in follow up patch sets.

Original change's description:
> Revert "Add MainSettingsFragmentTest"
>
> This reverts commit 8aee0918.
>
> Reason for revert: Test being added is flaky. See
> https://bugs.chromium.org/p/chromium/issues/detail?id=1066619
>
> Original change's description:
> > Add MainSettingsFragmentTest
> >
> > MainSettings.java have bit less test coverage over some of the
> > preferences, for example, the HomepageSettings at this moment. Adding
> > MainSettingsFragmentTest is aiming for more test coverage for the
> > list of preferences on the settings screen.
> >
> > Bug: 1052060, 1066362
> > Change-Id: Ib51c133f2a73f4ec85cc185c4101833bc3fa0b58
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2124729
> > Commit-Queue: Wenyu Fu <wenyufu@chromium.org>
> > Reviewed-by: Theresa  <twellington@chromium.org>
> > Reviewed-by: Natalie Chouinard <chouinard@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#754957}
>
> TBR=twellington@chromium.org,wychen@chromium.org,chouinard@chromium.org,wenyufu@chromium.org
>
> Change-Id: If15e22de962484fc87b3b5dc5eb1cfcf550cf024
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 1052060, 1066362
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2131017
> Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
> Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#755115}

TBR=twellington@chromium.org,wychen@chromium.org,rbpotter@chromium.org,chouinard@chromium.org,wenyufu@chromium.org

Change-Id: I0404143a0d074621d2433a5329ff6db9d7f41d73
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1052060, 1066362
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2130774Reviewed-by: Theresa  <twellington@chromium.org>
Commit-Queue: Wenyu Fu <wenyufu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#755406}

chrome/android/chrome_test_java_sources.gni

@@ -428,6 +428,7 @@ chrome_test_java_sources = [
   "javatests/src/org/chromium/chrome/browser/searchwidget/SearchActivityTest.java",
   "javatests/src/org/chromium/chrome/browser/searchwidget/SearchWidgetProviderTest.java",
   "javatests/src/org/chromium/chrome/browser/services/GoogleServicesManagerIntegrationTest.java",
+  "javatests/src/org/chromium/chrome/browser/settings/MainSettingsFragmentTest.java",
   "javatests/src/org/chromium/chrome/browser/settings/SettingsActivityTest.java",
   "javatests/src/org/chromium/chrome/browser/settings/homepage/HomepageSettingsFragmentTest.java",
   "javatests/src/org/chromium/chrome/browser/settings/homepage/HomepageSettingsFragmentWithEditorTest.java",

chrome/android/java/src/org/chromium/chrome/browser/settings/MainSettings.java

@@ -56,7 +56,6 @@ public class MainSettings extends PreferenceFragmentCompat
     public static final String PREF_UI_THEME = "ui_theme";
     public static final String PREF_DATA_REDUCTION = "data_reduction";
     public static final String PREF_NOTIFICATIONS = "notifications";
-    public static final String PREF_LANGUAGES = "languages";
     public static final String PREF_DOWNLOADS = "downloads";
     public static final String PREF_DEVELOPER = "developer";
 

chrome/android/java/src/org/chromium/chrome/browser/tracing/settings/DeveloperSettings.java

@@ -6,6 +6,7 @@ package org.chromium.chrome.browser.tracing.settings;
 
 import android.os.Bundle;
 
+import androidx.annotation.VisibleForTesting;
 import androidx.preference.PreferenceFragmentCompat;
 
 import org.chromium.chrome.R;
@@ -25,9 +26,13 @@ public class DeveloperSettings extends PreferenceFragmentCompat {
     // Non-translated strings:
     private static final String MSG_DEVELOPER_OPTIONS_TITLE = "Developer options";
 
+    private static Boolean sIsEnabledForTests;
+
     public static boolean shouldShowDeveloperSettings() {
         // Always enabled on canary, dev and local builds, otherwise can be enabled by tapping the
         // Chrome version in Settings>About multiple times.
+        if (sIsEnabledForTests != null) return sIsEnabledForTests;
+
         if (VersionConstants.CHANNEL <= Channel.DEV) return true;
         return SharedPreferencesManager.getInstance().readBoolean(
                 ChromePreferenceKeys.SETTINGS_DEVELOPER_ENABLED, false);
@@ -38,6 +43,11 @@ public class DeveloperSettings extends PreferenceFragmentCompat {
                 ChromePreferenceKeys.SETTINGS_DEVELOPER_ENABLED, true);
     }
 
+    @VisibleForTesting
+    public static void setIsEnabledForTests(Boolean isEnabled) {
+        sIsEnabledForTests = isEnabled;
+    }
+
     @Override
     public void onCreatePreferences(Bundle savedInstanceState, String s) {
         getActivity().setTitle(MSG_DEVELOPER_OPTIONS_TITLE);