Remove sign in preference in demo mode

BUG=632379

Review-Url: https://codereview.chromium.org/2195563002
Cr-Commit-Position: refs/heads/master@{#408738}

chrome/android/java/src/org/chromium/chrome/browser/preferences/MainPreferences.java

@@ -11,6 +11,7 @@ import android.os.Handler;
 import android.preference.Preference;
 import android.preference.PreferenceFragment;
 
+import org.chromium.base.ApiCompatibilityUtils;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.blimp_public.BlimpClientContext;
 import org.chromium.chrome.R;
@@ -55,6 +56,7 @@ public class MainPreferences extends PreferenceFragment implements SignInStateOb
     private ManagedPreferenceDelegate mManagedPreferenceDelegate;
 
     private boolean mShowSearchEnginePicker;
+    private boolean mIsDemoUser;
 
     public MainPreferences() {
         setHasOptionsMenu(true);
@@ -69,17 +71,21 @@ public class MainPreferences extends PreferenceFragment implements SignInStateOb
                 && getArguments().getBoolean(EXTRA_SHOW_SEARCH_ENGINE_PICKER, false)) {
             mShowSearchEnginePicker = true;
         }
+
+        mIsDemoUser = ApiCompatibilityUtils.isDemoUser(getActivity());
     }
 
     @Override
     public void onResume() {
         super.onResume();
-        SigninManager.get(getActivity()).addSignInStateObserver(this);
-
         // updatePreferences() must be called before setupSignInPref as updatePreferences loads
         // the SignInPreference.
         updatePreferences();
-        setupSignInPref();
+
+        if (!mIsDemoUser) {
+            SigninManager.get(getActivity()).addSignInStateObserver(this);
+            setupSignInPref();
+        }
 
         if (mShowSearchEnginePicker) {
             mShowSearchEnginePicker = false;
@@ -90,8 +96,10 @@ public class MainPreferences extends PreferenceFragment implements SignInStateOb
     @Override
     public void onPause() {
         super.onPause();
-        SigninManager.get(getActivity()).removeSignInStateObserver(this);
-        clearSignInPref();
+        if (!mIsDemoUser) {
+            SigninManager.get(getActivity()).removeSignInStateObserver(this);
+            clearSignInPref();
+        }
     }
 
     @Override
@@ -160,6 +168,10 @@ public class MainPreferences extends PreferenceFragment implements SignInStateOb
         } else {
             getPreferenceScreen().removePreference(dataReduction);
         }
+
+        if (mIsDemoUser) {
+            getPreferenceScreen().removePreference(findPreference(PREF_SIGN_IN));
+        }
     }
 
     private void setOnOffSummary(Preference pref, boolean isOn) {