Use 'pssh' data to determine key_id properly

media/cdm/cenc_utils.cc

Index: media/cdm/cenc_utils.cc
diff --git a/media/cdm/cenc_utils.cc b/media/cdm/cenc_utils.cc
index 86779b2174092ce5d0e3b5f5dca6a9c2f965c912..2e08c79d05dbbff8a8b59079bd8e031d86cf4844 100644
--- a/media/cdm/cenc_utils.cc
+++ b/media/cdm/cenc_utils.cc
@@ -170,11 +170,7 @@ bool GetKeyIdsForCommonSystemId(const std::vector<uint8_t>& input,
   }
 
   key_ids->swap(result);
-
-  // TODO(jrummell): This should return true only if there was at least one
-  // key ID present. However, numerous test files don't contain the 'pssh' box
-  // for Common Format, so no keys are found. http://crbug.com/460308
-  return true;
+  return key_ids->size() > 0;
 }
 
 }  // namespace media