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..9a40f7d162087505aa7f520ce0425fd33ecc3fd1 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::RecordACalled() {
+  EXPECT_FALSE(expecting_b_);
+  expecting_b_ = true;
+}
+
+void MatchingCallbackVerifier::RecordBCalled() {
+  EXPECT_TRUE(expecting_b_);
+  expecting_b_ = false;
+}
+
 }  // namespace media