title: "must have a dependency on com.google.firebase:firebase-core" but I have one
body: <p>I'm trying to update cordova plugins, and I'm getting this warning:</p>
  
  <pre><code>The app gradle file must have a dependency on com.google.firebase:firebase-core for Firebase services to work as intended.
  </code></pre>
  
  <p>It appears just as a warning. (Due to an unrelated problem, I unfortunately cannot test if the app works fine or not.)</p>
  
  <p>The thing is, I do have a dependency on it;</p>
  
  <pre><code>
  apply plugin: 'com.android.application'
  
  buildscript {
      repositories {
          mavenCentral()
          maven {
              url "https://maven.google.com"
          }
          jcenter()
      }
  
      dependencies {
          classpath 'com.android.tools.build:gradle:3.0.1'
          classpath 'com.google.gms:google-services:4.1.0'
          classpath 'com.google.firebase:firebase-core:11.6.2'
      }
  }
  
  // ...
  
  dependencies {
      implementation fileTree(dir: 'libs', include: '*.jar')
      // SUB-PROJECT DEPENDENCIES START
      implementation 'com.google.firebase:firebase-core:11.6.2'
      implementation(project(path: ":CordovaLib"))
      compile "com.android.support:support-v13:27.+"
      compile "me.leolin:ShortcutBadger:1.1.17@aar"
      compile "com.google.firebase:firebase-messaging:11.6.2"
      compile "com.squareup.okhttp3:okhttp:3.9.1"
      compile "com.android.support:support-v4:24.1.1+"
      // SUB-PROJECT DEPENDENCIES END
  }
  
  // ...
  
  apply plugin: 'com.google.gms.google-services'
  </code></pre>
  
  <p>What could cause this warning?</p>