Default emergency gesture setting On.

And a few drive-by fixes:
* Move all emergency gesture fragments and controllers to emergency
  package for better code colocation.
* Remove the placeholder video preference from emergency_gesture_settings.xml

Bug: 178009196
Test: reran robotests
Change-Id: Ifcb591e7ab8e5e5494c480cbbe9410c08c296f8e

src/com/android/settings/emergency/EmergencyGestureNumberOverridePreferenceController.java

@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.emergency;
+
+import static com.android.settingslib.emergencynumber.EmergencyNumberUtils.EMERGENCY_NUMBER_OVERRIDE_AUTHORITY;
+
+import android.content.Context;
+import android.database.ContentObserver;
+import android.os.Handler;
+import android.os.Looper;
+import android.telephony.PhoneNumberUtils;
+import android.text.Spannable;
+
+import androidx.annotation.VisibleForTesting;
+import androidx.preference.Preference;
+import androidx.preference.PreferenceScreen;
+
+import com.android.settings.R;
+import com.android.settings.core.BasePreferenceController;
+import com.android.settingslib.core.lifecycle.LifecycleObserver;
+import com.android.settingslib.core.lifecycle.events.OnStart;
+import com.android.settingslib.core.lifecycle.events.OnStop;
+import com.android.settingslib.emergencynumber.EmergencyNumberUtils;
+
+/**
+ * Preference controller for emergency gesture number override.
+ */
+public class EmergencyGestureNumberOverridePreferenceController extends BasePreferenceController
+        implements LifecycleObserver, OnStart, OnStop {
+
+    @VisibleForTesting
+    EmergencyNumberUtils mEmergencyNumberUtils;
+    private final Handler mHandler;
+    private final ContentObserver mSettingsObserver;
+    private Preference mPreference;
+
+    public EmergencyGestureNumberOverridePreferenceController(Context context,
+            String preferenceKey) {
+        super(context, preferenceKey);
+        mEmergencyNumberUtils = new EmergencyNumberUtils(context);
+        mHandler = new Handler(Looper.getMainLooper());
+        mSettingsObserver = new EmergencyGestureNumberOverrideSettingsObserver(mHandler);
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        return mContext.getResources()
+                .getBoolean(R.bool.config_show_emergency_gesture_settings) ? AVAILABLE
+                : UNSUPPORTED_ON_DEVICE;
+    }
+
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        super.displayPreference(screen);
+
+        mPreference = screen.findPreference(getPreferenceKey());
+    }
+
+    @Override
+    public CharSequence getSummary() {
+        String number = mEmergencyNumberUtils.getPoliceNumber();
+        String summary = mContext.getString(R.string.emergency_gesture_call_for_help_summary,
+                number);
+        int numberStartIndex = summary.indexOf(number);
+        if (numberStartIndex < 0) {
+            return summary;
+        }
+        Spannable summarySpan = Spannable.Factory.getInstance().newSpannable(summary);
+        PhoneNumberUtils.addTtsSpan(summarySpan, numberStartIndex,
+                numberStartIndex + number.length());
+        return summarySpan;
+    }
+
+    @Override
+    public void onStart() {
+        mContext.getContentResolver().registerContentObserver(EMERGENCY_NUMBER_OVERRIDE_AUTHORITY,
+                false, mSettingsObserver);
+    }
+
+    @Override
+    public void onStop() {
+        mContext.getContentResolver().unregisterContentObserver(mSettingsObserver);
+    }
+
+    private class EmergencyGestureNumberOverrideSettingsObserver extends ContentObserver {
+        EmergencyGestureNumberOverrideSettingsObserver(Handler h) {
+            super(h);
+        }
+
+        @Override
+        public void onChange(boolean selfChange) {
+            if (mPreference != null) {
+                updateState(mPreference);
+            }
+        }
+    }
+}