Address outstanding comments from CL 10384140

base/base64.cc

Index: base/base64.cc
diff --git a/base/base64.cc b/base/base64.cc
index 62bd12d1fb635f951f4ce7d2aa692cfb5a65aeab..f2c68230e3545f9175f5a391fa24b4f797841127 100644
--- a/base/base64.cc
+++ b/base/base64.cc
@@ -14,7 +14,9 @@ bool Base64Encode(const StringPiece& input, std::string* output) {
 
   // null terminates result since result is base64 text!
   int input_size = static_cast<int>(input.size());
-  int output_size= modp_b64_encode(&(temp[0]), input.data(), input_size);
+
+  // modp_b64_encode_len() returns at least 1, so temp[0] is safe to use.
+  int output_size = modp_b64_encode(&(temp[0]), input.data(), input_size);
   if (output_size < 0)
     return false;