restore java version detection for android & plugins sdks (IDEA-187506)

java/openapi/src/com/intellij/openapi/projectRoots/JavaSdkVersionUtil.java

@@ -22,7 +22,17 @@ public class JavaSdkVersionUtil {
   }
 
   public static JavaSdkVersion getJavaSdkVersion(@Nullable Sdk sdk) {
-    return sdk != null && sdk.getSdkType() instanceof JavaSdk ? ((JavaSdk)sdk.getSdkType()).getVersion(sdk) : null;
+    if (sdk != null) {
+      SdkTypeId sdkType = sdk.getSdkType();
+      if (!(sdkType instanceof JavaSdk) && sdkType instanceof SdkType) {
+        sdkType = ((SdkType)sdkType).getDependencyType();
+      }
+
+      if (sdkType instanceof JavaSdk) {
+        return ((JavaSdk)sdkType).getVersion(sdk);
+      }
+    }
+    return null;
   }
 
   @Nullable

platform/lang-api/src/com/intellij/openapi/projectRoots/SdkType.java

@@ -225,6 +225,15 @@ public abstract class SdkType implements SdkTypeId {
     throw new IllegalArgumentException("Unknown SDk type: " + sdkTypeClass);
   }
 
+  /**
+   * @return for sdk build over another sdk, returns type of the nested sdk, 
+   *         e.g. plugins or android sdks are build over java sdk and for them the method returns {@link JavaSdkType},
+   *         null otherwise
+   */
+  protected SdkType getDependencyType() {
+    return null;
+  }
+
   public boolean isRootTypeApplicable(@NotNull OrderRootType type) {
     return true;
   }