Constructor with Graph for TensorFlowInferenceInterface (#12669)

Added a new Constructor with `Graph` object only, it will be very useful when user is doing some custom graph loading.

Signature:
`public TensorFlowInferenceInterface(Graph g)`

tensorflow/contrib/android/java/org/tensorflow/contrib/android/TensorFlowInferenceInterface.java

@@ -160,6 +160,22 @@ public class TensorFlowInferenceInterface {
     }
   }
   
+  /*
+   * Construct a TensorFlowInferenceInterface with provided Graph
+   *
+   * @param g The Graph to use to construct this interface.
+   */
+  public TensorFlowInferenceInterface(Graph g) {
+    prepareNativeRuntime();
+      
+    // modelName is redundant here, here is for
+    // avoiding error in initialization as modelName is marked final.
+    this.modelName = "";
+    this.g = g;
+    this.sess = new Session(g);
+    this.runner = sess.runner();
+  }
+
   /**
    * Runs inference between the previously registered input nodes (via feed*) and the requested
    * output nodes. Output nodes can then be queried with the fetch* methods.