Support for using Signal without Play Services

This is now possible with beta calling, so non-GCM users are a
part of beta calling by default.

// FREEBIE

src/org/thoughtcrime/securesms/components/reminder/DozeReminder.java

@@ -0,0 +1,48 @@
+package org.thoughtcrime.securesms.components.reminder;
+
+
+import android.content.Context;
+import android.content.Intent;
+import android.net.Uri;
+import android.os.Build;
+import android.os.PowerManager;
+import android.provider.Settings;
+import android.support.annotation.NonNull;
+import android.support.annotation.RequiresApi;
+import android.view.View;
+
+import org.thoughtcrime.securesms.util.TextSecurePreferences;
+
+public class DozeReminder extends Reminder {
+
+  @RequiresApi(api = Build.VERSION_CODES.M)
+  public DozeReminder(@NonNull final Context context) {
+    super("Optimize for missing Play Services",
+          "This device does not support Play Services. Tap to disable system battery optimizations that prevent Signal from retrieving messages while inactive.");
+
+    setOkListener(new View.OnClickListener() {
+      @Override
+      public void onClick(View v) {
+        TextSecurePreferences.setPromptedOptimizeDoze(context, true);
+        Intent intent = new Intent(Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS,
+                                   Uri.parse("package:" + context.getPackageName()));
+        context.startActivity(intent);
+      }
+    });
+
+    setDismissListener(new View.OnClickListener() {
+      @Override
+      public void onClick(View v) {
+        TextSecurePreferences.setPromptedOptimizeDoze(context, true);
+      }
+    });
+  }
+
+  public static boolean isEligible(Context context) {
+    return TextSecurePreferences.isGcmDisabled(context)            &&
+           !TextSecurePreferences.hasPromptedOptimizeDoze(context) &&
+           Build.VERSION.SDK_INT >= Build.VERSION_CODES.M          &&
+           !((PowerManager)context.getSystemService(Context.POWER_SERVICE)).isIgnoringBatteryOptimizations(context.getPackageName());
+  }
+
+}