feat(android): remove RequiresApi annotation and drop support for API 19 (#540)

BREAKING CHANGE: Drop Android 4.4 support (SDK API level 19). Min required is 21.

Author: nphyatt

plugin.xml

@@ -52,8 +52,6 @@
     <source-file src="src/android/com/ionicframework/cordova/webview/AndroidProtocolHandler.java" target-dir="src/com/ionicframework/cordova/webview"/>
     <source-file src="src/android/com/ionicframework/cordova/webview/UriMatcher.java" target-dir="src/com/ionicframework/cordova/webview"/>
     <source-file src="src/android/com/ionicframework/cordova/webview/WebViewLocalServer.java" target-dir="src/com/ionicframework/cordova/webview"/>
-    <preference name="ANDROID_SUPPORT_ANNOTATIONS_VERSION" default="27.+"/>
-    <framework src="com.android.support:support-annotations:$ANDROID_SUPPORT_ANNOTATIONS_VERSION"/>
   </platform>
 
   <!-- ios -->

src/android/com/ionicframework/cordova/webview/IonicWebViewEngine.java

@@ -4,11 +4,9 @@
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.content.pm.PackageInfo;
-import android.annotation.TargetApi;
 import android.graphics.Bitmap;
 import android.net.Uri;
 import android.os.Build;
-import android.support.annotation.RequiresApi;
 import android.util.Log;
 import android.webkit.ServiceWorkerController;
 import android.webkit.ServiceWorkerClient;
@@ -134,18 +132,11 @@ public ServerClient(SystemWebViewEngine parentEngine, ConfigXmlParser parser) {
       this.parser = parser;
     }
 
-    @RequiresApi(Build.VERSION_CODES.LOLLIPOP)
     @Override
     public WebResourceResponse shouldInterceptRequest(WebView view, WebResourceRequest request) {
       return localServer.shouldInterceptRequest(request.getUrl(), request);
     }
 
-    @TargetApi(Build.VERSION_CODES.KITKAT)
-    @Override
-    public WebResourceResponse shouldInterceptRequest(WebView view, String url) {
-      return localServer.shouldInterceptRequest(Uri.parse(url), null);
-    }
-
     @Override
     public void onPageStarted(WebView view, String url, Bitmap favicon) {
       super.onPageStarted(view, url, favicon);