Re-add PlatformSpecific.isAppEngine() for backwards-compatibility

hystrix-core/src/main/java/com/netflix/hystrix/util/PlatformSpecific.java

@@ -19,48 +19,57 @@
 import java.util.concurrent.ThreadFactory;
 
 public class PlatformSpecific {
-    private final boolean isAppEngineStandardEnvironment;
+    private final Platform platform;
+
+    private enum Platform {
+        STANDARD, APPENGINE_STANDARD, APPENGINE_FLEXIBLE
+    }
 
     private static PlatformSpecific INSTANCE = new PlatformSpecific();
 
     private PlatformSpecific() {
-        isAppEngineStandardEnvironment = determineAppEngineReflectively();
+        platform = determinePlatformReflectively();
     }
 
     public static boolean isAppEngineStandardEnvironment() {
-        return INSTANCE.isAppEngineStandardEnvironment;
+        return INSTANCE.platform == Platform.APPENGINE_STANDARD;
+    }
+
+    public static boolean isAppEngine() {
+        return INSTANCE.platform == Platform.APPENGINE_FLEXIBLE || INSTANCE.platform == Platform.APPENGINE_STANDARD;
     }
 
     /*
      * This detection mechanism is from Guava - specifically
      * http://docs.guava-libraries.googlecode.com/git/javadoc/src-html/com/google/common/util/concurrent/MoreExecutors.html#line.766
      * Added GAE_LONG_APP_ID check to detect only AppEngine Standard Environment
      */
-    private static boolean determineAppEngineReflectively() {
+    private static Platform determinePlatformReflectively() {
         if (System.getProperty("com.google.appengine.runtime.environment") == null) {
-            return false;
+            return Platform.STANDARD;
         }
         // GAE_LONG_APP_ID is only set in the GAE Flexible Environment, where we want standard threading
         if (System.getenv("GAE_LONG_APP_ID") != null) {
-            return false;
+            return Platform.APPENGINE_FLEXIBLE;
         }
         try {
             // If the current environment is null, we're not inside AppEngine.
-            return Class.forName("com.google.apphosting.api.ApiProxy")
+            boolean isInsideAppengine = Class.forName("com.google.apphosting.api.ApiProxy")
                     .getMethod("getCurrentEnvironment")
                     .invoke(null) != null;
+            return isInsideAppengine ? Platform.APPENGINE_STANDARD : Platform.STANDARD;
         } catch (ClassNotFoundException e) {
             // If ApiProxy doesn't exist, we're not on AppEngine at all.
-            return false;
+            return Platform.STANDARD;
         } catch (InvocationTargetException e) {
             // If ApiProxy throws an exception, we're not in a proper AppEngine environment.
-            return false;
+            return Platform.STANDARD;
         } catch (IllegalAccessException e) {
             // If the method isn't accessible, we're not on a supported version of AppEngine;
-            return false;
+            return Platform.STANDARD;
         } catch (NoSuchMethodException e) {
             // If the method doesn't exist, we're not on a supported version of AppEngine;
-            return false;
+            return Platform.STANDARD;
         }
     }