NameScope interacts poorly with subscoping

System information

• Have I written custom code (as opposed to using a stock example script provided in TensorFlow): Yes
• OS Platform and Distribution (e.g., Linux Ubuntu 16.04 x86_64): macOS x86_64
• TensorFlow installed from (source or binary): source
• TensorFlow version (use command below): 0.5.0-SNAPSHOT
• Java version (i.e., the output of java -version): JDK 11

Describe the current behavior
I'm trying to debug test failures in tensorflow-framework, and noticed that the test sessions use tf = Ops.create(graph).withName("test");. This makes all the nodes have the name "test_" which makes things pretty tricky to debug. I changed it to tf = Ops.create(graph).withSubScope("test");, but now I'm getting test failures out of the optimizers with the following message:

[INFO] Running org.tensorflow.framework.optimizers.FtrlTest
[ERROR] Tests run: 5, Failures: 0, Errors: 4, Skipped: 0, Time elapsed: 0.455 s <<< FAILURE! - in org.tensorflow.framework.optimizers.FtrlTest
[ERROR] testFtrlWithL1  Time elapsed: 0.415 s  <<< ERROR!
java.lang.IllegalArgumentException: invalid name: 'test/var0_gradient_accumulator' does not match the regular expression [A-Za-z0-9.][A-Za-z0-9_.\-]*
	at org.tensorflow.framework.optimizers.FtrlTest.testFtrlWithL1(FtrlTest.java:166)

Describe the expected behavior

No test failures, and test nodes have the correct op names.

Code to reproduce the issue
Make the withSubScope change at line 44 in org.tensorflow.framework.utils.GraphTestSession.

tensorflow-framework の GraphTestSession の 44 行目から開始し、Ops.withName("test") と Ops.withSubScope("test") の動作を比較します。166 行目の FtrlTest.testFtrlWithL1 で失敗を再現し、生成された名前と、それに関係する名前の検証を調べます。オプティマイザのテストがパスし、テストノードがデバッグ可能で有効な Op 名を保持すれば完了です。