Be more comprehensive about boot time RTC check

import android.database.ContentObserver;

import android.net.Uri;

import android.os.Binder;

import android.os.Build;

import android.os.Bundle;

import android.os.Environment;

import android.os.Handler;

        // because kernel doesn't keep this after reboot

        setTimeZoneImpl(SystemProperties.get(TIMEZONE_PROPERTY));

        // Also sure that we're booting with a halfway sensible current time

        if (mNativeData != 0) {

            final long systemBuildTime = Environment.getRootDirectory().lastModified();

            // Ensure that we're booting with a halfway sensible current time.  Use the

            // most recent of Build.TIME, the root file system's timestamp, and the

            // value of the ro.build.date.utc system property (which is in seconds).

            final long systemBuildTime =  Long.max(

                    1000L * SystemProperties.getLong("ro.build.date.utc", -1L),

                    Long.max(Environment.getRootDirectory().lastModified(), Build.TIME));

            if (System.currentTimeMillis() < systemBuildTime) {

                Slog.i(TAG, "Current time only " + System.currentTimeMillis()

                        + ", advancing to build time " + systemBuildTime);