alvareztech/MainActivity.java

## activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="tech.alvarez.ejemplowebview.MainActivity">

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="abrirPaginaWeb"
        android:text="@string/abrir_pagina_web" />

    <WebView
        android:id="@+id/paginaWebView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

## build.gradle
apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.0"
    defaultConfig {
        applicationId "tech.alvarez.ejemplowebview"
        minSdkVersion 15
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:25.0.0'
    testCompile 'junit:junit:4.12'

    compile 'com.android.support:customtabs:25.0.0'
}

## MainActivity.java
package tech.alvarez.ejemplowebview;

import android.net.Uri;
import android.support.customtabs.CustomTabsIntent;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.webkit.WebView;

public class MainActivity extends AppCompatActivity {

    private WebView paginaWebView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        paginaWebView = (WebView) findViewById(R.id.paginaWebView);

//        paginaWebView.loadUrl("http://alvarez.tech/android-umsa");

        String html = "<html><body><h2>Ejemplo</h2><p>Este es un contenido de ejemplo</p></body></html>";

        paginaWebView.loadData(html, "text/html; charset-utf-8", null);


    }

    public void abrirPaginaWeb(View view) {

        String url = "http://alvarez.tech/android-umsa";

        CustomTabsIntent.Builder builder = new CustomTabsIntent.Builder();
        builder.setToolbarColor(ContextCompat.getColor(this, R.color.colorPrimary));

        CustomTabsIntent customTabsIntent = builder.build();

        customTabsIntent.launchUrl(this, Uri.parse(url));

    }
}
	<?xml version="1.0" encoding="utf-8"?>
	<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	xmlns:tools="http://schemas.android.com/tools"
	android:id="@+id/activity_main"
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	android:orientation="vertical"
	android:paddingBottom="@dimen/activity_vertical_margin"
	android:paddingLeft="@dimen/activity_horizontal_margin"
	android:paddingRight="@dimen/activity_horizontal_margin"
	android:paddingTop="@dimen/activity_vertical_margin"
	tools:context="tech.alvarez.ejemplowebview.MainActivity">

	<Button
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:onClick="abrirPaginaWeb"
	android:text="@string/abrir_pagina_web" />

	<WebView
	android:id="@+id/paginaWebView"
	android:layout_width="match_parent"
	android:layout_height="match_parent" />

	</LinearLayout>
	apply plugin: 'com.android.application'

	android {
	compileSdkVersion 25
	buildToolsVersion "25.0.0"
	defaultConfig {
	applicationId "tech.alvarez.ejemplowebview"
	minSdkVersion 15
	targetSdkVersion 25
	versionCode 1
	versionName "1.0"
	testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
	}
	buildTypes {
	release {
	minifyEnabled false
	proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
	}
	}
	}

	dependencies {
	compile fileTree(dir: 'libs', include: ['*.jar'])
	androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
	exclude group: 'com.android.support', module: 'support-annotations'
	})
	compile 'com.android.support:appcompat-v7:25.0.0'
	testCompile 'junit:junit:4.12'

	compile 'com.android.support:customtabs:25.0.0'
	}
	package tech.alvarez.ejemplowebview;

	import android.net.Uri;
	import android.support.customtabs.CustomTabsIntent;
	import android.support.v4.content.ContextCompat;
	import android.support.v7.app.AppCompatActivity;
	import android.os.Bundle;
	import android.view.View;
	import android.webkit.WebView;

	public class MainActivity extends AppCompatActivity {

	private WebView paginaWebView;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
	setContentView(R.layout.activity_main);

	paginaWebView = (WebView) findViewById(R.id.paginaWebView);

	// paginaWebView.loadUrl("http://alvarez.tech/android-umsa");

	String html = "<html><body><h2>Ejemplo</h2><p>Este es un contenido de ejemplo</p></body></html>";

	paginaWebView.loadData(html, "text/html; charset-utf-8", null);


	}

	public void abrirPaginaWeb(View view) {

	String url = "http://alvarez.tech/android-umsa";

	CustomTabsIntent.Builder builder = new CustomTabsIntent.Builder();
	builder.setToolbarColor(ContextCompat.getColor(this, R.color.colorPrimary));

	CustomTabsIntent customTabsIntent = builder.build();

	customTabsIntent.launchUrl(this, Uri.parse(url));

	}
	}