Fix canPlayType() support for non-RFC compliant mp3 mimetype.

net/base/mime_util.cc

Index: net/base/mime_util.cc
diff --git a/net/base/mime_util.cc b/net/base/mime_util.cc
index 9d15256172ff9fc99f2a5c9e27021cfd785a6263..5062ab54b2e5224a953affbbd18bc38e0bdd231d 100644
--- a/net/base/mime_util.cc
+++ b/net/base/mime_util.cc
@@ -473,7 +473,11 @@ static const MediaFormatStrict format_codec_mappings[] = {
   { "video/ogg", "opus,theora,vorbis" },
   { "audio/ogg", "opus,vorbis" },
   { "application/ogg", "opus,theora,vorbis" },
-  { "audio/mpeg", "" },
+  { "audio/mpeg", ",mp3" }, // Note: Empty string codec ID indicates

[DaleCurtis, 2014/07/17 18:41:55]

I'm not convinced it's a good idea, but I wonder if a magic word like ::EMPTY::
would be better in this case.  It wasn't immediately clear that you meant the
prefixed comma was providing the empty string. 

[acolwell GONE FROM CHROMIUM, 2014/07/17 18:57:00]

I agree that this isn't awesome, but I fear some sort of "special" string might
lead to other problems if someone is crafty about what they pass to
canPlayType(). I've updated the comment to clarify what is going on with the
comma at the beginning so hopefully that helps.

+                            // a missing codecs= parameter is also valid.
+                            // The presense of 'mp3' is not RFC compliant,
+                            // but is common in the wild so it is a defacto
+                            // standard.
   { "audio/mp3", "" },
   { "audio/x-mp3", "" }
 };
@@ -519,11 +523,18 @@ bool MimeUtil::AreSupportedCodecs(const MimeMappings& supported_codecs,
   if (supported_codecs.empty())
     return codecs.empty();
 
+  // If no codecs are specified in the mimetype, check to see if a missing
+  // codecs parameter is allowed.
+  if (codecs.empty())
+    return supported_codecs.find("") != supported_codecs.end();

[Ryan Sleevi, 2014/07/17 18:38:08]

.find(std::string())

[acolwell GONE FROM CHROMIUM, 2014/07/17 18:57:00]

Done.

+
   for (size_t i = 0; i < codecs.size(); ++i) {
-    if (supported_codecs.find(codecs[i]) == supported_codecs.end())
+    if (supported_codecs.find(codecs[i]) == supported_codecs.end() ||
+        codecs[i].empty())

[Ryan Sleevi, 2014/07/17 18:38:08]

Do the .empty() check before the .find(), and avoid the lookup.

[acolwell GONE FROM CHROMIUM, 2014/07/17 18:57:00]

Done.

       return false;
   }
-  return !codecs.empty();
+
+  return true;
 }
 
 // Checks all the codecs present in the |codecs| against the entries in