Fix warning about unexpected mock function call.

BUG=angleproject:985

Change-Id: If2138d8ec9a4f99adaf4ef1a4cbeeab6b0bf9f2c
Reviewed-on: https://chromium-review.googlesource.com/267349
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/TransformFeedback_unittest.cpp b/src/libANGLE/TransformFeedback_unittest.cpp
index f65527e..baddfb7 100644
--- a/src/libANGLE/TransformFeedback_unittest.cpp
+++ b/src/libANGLE/TransformFeedback_unittest.cpp
@@ -98,6 +98,8 @@
     static const size_t bindIndex = 0;
 
     rx::MockTransformFeedbackImpl *feedbackImpl = new rx::MockTransformFeedbackImpl;
+    EXPECT_CALL(*feedbackImpl, destructor()).Times(1).RetiresOnSaturation();
+
     gl::TransformFeedback *feedback = new gl::TransformFeedback(feedbackImpl, 1, mCaps);
 
     EXPECT_EQ(feedback->getIndexedBufferCount(), mCaps.maxTransformFeedbackSeparateAttributes);