Bug 1577021: Add test coverage for non-ascii characters in MimeType codecs. r=dminor

Provides coverage for an issue fixed in 1573381. Note that while that bug
discusses big endian machines, the tests added will cover both the big and
little endian case of the bug. This is because we have test cases that make sure
both octets of 16 wide char are being correctly compared.

Differential Revision: https://phabricator.services.mozilla.com/D44054

--HG--
extra : moz-landing-system : lando

dom/media/gtest/TestMediaMIMETypes.cpp

@@ -154,6 +154,30 @@ TEST(MediaMIMETypes, MediaCodecs)
   EXPECT_TRUE(two.ContainsAll(two));
   EXPECT_TRUE(two.ContainsAll(one));
   EXPECT_FALSE(one.ContainsAll(two));
+
+  // Check wide char case where both octets/bytes are relevant. Note we don't
+  // use `EqualsLiteral` here because at the time of writing it will place the
+  // literal into a narrow string which then doesn't compare correctly with
+  // the wide representation from MediaCodecs.
+  MediaCodecs euroSign(u8" € ");  // U+20AC
+  EXPECT_FALSE(euroSign.IsEmpty());
+  EXPECT_TRUE(euroSign.AsString().Equals(NS_LITERAL_STRING(" € ")));
+  EXPECT_FALSE(euroSign.Contains(NS_LITERAL_STRING("")));
+  EXPECT_TRUE(euroSign.Contains(NS_LITERAL_STRING("€")));
+  EXPECT_FALSE(euroSign.Contains(NS_LITERAL_STRING("€€")));
+  EXPECT_TRUE(euroSign.ContainsPrefix(NS_LITERAL_STRING("")));
+  EXPECT_TRUE(euroSign.ContainsPrefix(NS_LITERAL_STRING("€")));
+  EXPECT_FALSE(euroSign.ContainsPrefix(
+      NS_LITERAL_STRING("₭")));  // U+20AD -- ensure second octet is compared
+  EXPECT_FALSE(euroSign.ContainsPrefix(
+      NS_LITERAL_STRING("↬")));  // U+21AC -- ensure first octet is compared
+  EXPECT_FALSE(euroSign.ContainsPrefix(NS_LITERAL_STRING("€ ")));
+  iterations = 0;
+  for (const auto& codec : euroSign.Range()) {
+    ++iterations;
+    EXPECT_TRUE(codec.Equals(NS_LITERAL_STRING("€")));
+  }
+  EXPECT_EQ(1, iterations);
 }
 
 TEST(MediaMIMETypes, MakeMediaExtendedMIMEType_bad)