Add more tests for H264 profile level id parsing

webrtc/common_video/h264/profile_level_id_unittest.cc

Index: webrtc/common_video/h264/profile_level_id_unittest.cc
diff --git a/webrtc/common_video/h264/profile_level_id_unittest.cc b/webrtc/common_video/h264/profile_level_id_unittest.cc
index 8bc50689d98479ae7566318939df1ffd34029b1c..491fda14aaf89fb80be630dcfef5d357832948df 100644
--- a/webrtc/common_video/h264/profile_level_id_unittest.cc
+++ b/webrtc/common_video/h264/profile_level_id_unittest.cc
@@ -75,7 +75,7 @@ TEST(H264ProfileLevelId, TestToString) {
                           kProfileConstrainedBaseline, kLevel3_1)));
   EXPECT_EQ("42000a",
             *ProfileLevelIdToString(ProfileLevelId(kProfileBaseline, kLevel1)));
-  EXPECT_EQ("4D001f",
+  EXPECT_EQ("4d001f",
             ProfileLevelIdToString(ProfileLevelId(kProfileMain, kLevel3_1)));
   EXPECT_EQ("640c2a", *ProfileLevelIdToString(
                           ProfileLevelId(kProfileConstrainedHigh, kLevel4_2)));
@@ -88,10 +88,19 @@ TEST(H264ProfileLevelId, TestToStringLevel1b) {
                           kProfileConstrainedBaseline, kLevel1_b)));
   EXPECT_EQ("42100b", *ProfileLevelIdToString(
                           ProfileLevelId(kProfileBaseline, kLevel1_b)));
-  EXPECT_EQ("4D100b",
+  EXPECT_EQ("4d100b",
             *ProfileLevelIdToString(ProfileLevelId(kProfileMain, kLevel1_b)));
 }
 
+TEST(H264ProfileLevelId, TestToStringRoundTrip) {
+  EXPECT_EQ("42e01f", *ProfileLevelIdToString(*ParseProfileLevelId("42e01f")));
+  EXPECT_EQ("42e01f", *ProfileLevelIdToString(*ParseProfileLevelId("42E01F")));
+  EXPECT_EQ("4d100b", *ProfileLevelIdToString(*ParseProfileLevelId("4d100b")));
+  EXPECT_EQ("4d100b", *ProfileLevelIdToString(*ParseProfileLevelId("4D100B")));
+  EXPECT_EQ("640c2a", *ProfileLevelIdToString(*ParseProfileLevelId("640c2a")));
+  EXPECT_EQ("640c2a", *ProfileLevelIdToString(*ParseProfileLevelId("640C2A")));
+}
+
 TEST(H264ProfileLevelId, TestToStringInvalid) {
   EXPECT_FALSE(ProfileLevelIdToString(ProfileLevelId(kProfileHigh, kLevel1_b)));
   EXPECT_FALSE(ProfileLevelIdToString(