Relax Base64 Decoding

Strict decoding breaks Base64 MIME encodings, which place newlines after
a certain number of spaces. MIME encoding is commonly used by Java
Clients.

src/json_request_translator.cc

@@ -146,12 +146,14 @@ JsonRequestTranslator::JsonRequestTranslator(
     stream_translator_.reset(new RequestStreamTranslator(
         *type_resolver, output_delimiters, std::move(request_info)));
     writer = stream_translator_.get();
+    writer->set_use_strict_base64_decoding(false);
     translated = stream_translator_.get();
   } else {
     // No streaming - use a RequestMessageTranslator
     message_translator_.reset(new RequestMessageTranslator(
         *type_resolver, output_delimiters, std::move(request_info)));
     writer = &message_translator_->Input();
+    writer->set_use_strict_base64_decoding(false);
     translated = message_translator_.get();
   }
   parser_.reset(new pbconv::JsonStreamParser(writer));

src/request_message_translator.cc

@@ -73,6 +73,9 @@ RequestMessageTranslator::RequestMessageTranslator(
     writer_pipeline_ = prefix_writer_.get();
   }
 
+  // Relax B64 to support MIME B64
+  writer_pipeline_->set_use_strict_base64_decoding(false);
+
   if (output_delimiter_) {
     // Reserve space for the delimiter at the begining of the message_
     ReserveDelimiterSpace();