Compartir páginas de Visualforce entre Classic y Lightning Experience

<apex:outputText value="This is Salesforce Classic."
    rendered="{! $User.UIThemeDisplayed() == 'Theme3' }"/>

<apex:outputPanel rendered="{! $User.UIThemeDisplayed == 'Theme3' }">
    <apex:outputText value="This is Salesforce Classic."/>
    <apex:outputText value="These are multiple components wrapped by an outputPanel."/>
</apex:outputPanel>
<apex:outputPanel rendered="{! $User.UIThemeDisplayed == 'Theme4d' }">
    <apex:outputText value="Everything is simpler in Lightning Experience."/>
</apex:outputPanel>

<apex:page standardController="Account">
    <!-- Salesforce Classic "Aloha" theme -->
    <apex:variable var="uiTheme" value="classic2010Theme"
        rendered="{!$User.UIThemeDisplayed == 'Theme3'}">
        <apex:stylesheet value="{!URLFOR($Resource.AppStyles,
                                         'classic-styling.css')}" />
    </apex:variable>
    <!-- Lightning Desktop theme -->
    <apex:variable var="uiTheme" value="lightningDesktop"
        rendered="{!$User.UIThemeDisplayed == 'Theme4d'}">
        <apex:stylesheet value="{!URLFOR($Resource.AppStyles,
                                         'lightning-styling.css')}" />
    </apex:variable>
    <!-- Salesforce mobile theme -->
    <apex:variable var="uiTheme" value="SalesforceApp"
        rendered="{!$User.UIThemeDisplayed == 'Theme4t'}">
        <apex:stylesheet value="{!URLFOR($Resource.AppStyles,
                                         'mobile-styling.css')}" />
    </apex:variable>
    <!-- Rest of your page -->
    <p>
        Value of $User.UIThemeDisplayed: {! $User.UIThemeDisplayed }
    </p>
</apex:page>

public with sharing class ForceUIExtension {
    // Empty constructor, required for Visualforce controller extension
    public ForceUIExtension(ApexPages.StandardController controller) { }
    // Simple accessors for the System.UserInfo theme methods
    public String getContextUserUiTheme() {
        return UserInfo.getUiTheme();
    }
    public String getContextUserUiThemeDisplayed() {
        return UserInfo.getUiThemeDisplayed();
    }
}

SELECT UserPreferencesLightningExperiencePreferred FROM User WHERE Id = 'CurrentUserId'

<apex:page>
<script src="/soap/ajax/36.0/connection.js" type="text/javascript"></script>
<script type="text/javascript">
    // Query for the preference value
    sforce.connection.sessionId = '{! $Api.Session_ID }';
    var uiPrefQuery = "SELECT Id, UserPreferencesLightningExperiencePreferred " +
                      "FROM User WHERE Id = '{! $User.Id }'";
    var userThemePreferenceResult = sforce.connection.query(uiPrefQuery);
    // Display the returned result on the page
    document.addEventListener('DOMContentLoaded', function(event){
        document.getElementById('userThemePreferenceResult').innerHTML =
            userThemePreferenceResult;
    });
</script>
<h1>userThemePreferenceResult (JSON)</h1>
<pre><span id="userThemePreferenceResult"/></pre>
</apex:page>