Allow setContentDecryptionModule() to get called when setting is done.

media/base/test_helpers.cc

Index: media/base/test_helpers.cc
diff --git a/media/base/test_helpers.cc b/media/base/test_helpers.cc
index 929b2f3c725c70ee4fa26fc770ee0e9e827112d6..8ae8baee185cd1eb5be502fd01da15ed9b8b0d25 100644
--- a/media/base/test_helpers.cc
+++ b/media/base/test_helpers.cc
@@ -242,4 +242,21 @@ bool VerifyFakeVideoBufferForTest(
           height == config.coded_size().height());
 }
 
+MatchingCallbackVerifier::MatchingCallbackVerifier() : expecting_B_(false) {
+}
+
+MatchingCallbackVerifier::~MatchingCallbackVerifier() {
+  EXPECT_FALSE(expecting_B_);
+}
+
+void MatchingCallbackVerifier::A() {
+  EXPECT_FALSE(expecting_B_);
+  expecting_B_ = true;
+}
+
+void MatchingCallbackVerifier::B() {
+  EXPECT_TRUE(expecting_B_);
+  expecting_B_ = false;
+}
+
 }  // namespace media