Fix CryptAuthApiCallFlow resulting in an error if the server returns an empty string.

components/proximity_auth/cryptauth/cryptauth_api_call_flow.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/proximity_auth/cryptauth/cryptauth_api_call_flow.h"
 
 #include "base/strings/string_number_conversions.h"
 #include "net/url_request/url_fetcher.h"
 
 namespace proximity_auth {
 
 namespace {
 
-const char kNoResponseBodyError[] = "No response body";
+const char kResponseBodyError[] = "Failed to get response body";
 const char kRequestFailedError[] = "Request failed";
 const char kHttpStatusErrorPrefix[] = "HTTP status: ";
 
 }  // namespace
 
 CryptAuthApiCallFlow::CryptAuthApiCallFlow(const GURL& request_url)
     : request_url_(request_url) {
 }
 
 CryptAuthApiCallFlow::~CryptAuthApiCallFlow() {
@@ skipping 18 matching lines @@
   return serialized_request_;
 }
 
 std::string CryptAuthApiCallFlow::CreateApiCallBodyContentType() {
   return "application/x-protobuf";
 }
 
 void CryptAuthApiCallFlow::ProcessApiCallSuccess(
     const net::URLFetcher* source) {
   std::string serialized_response;
-  if (!source->GetResponseAsString(&serialized_response) ||
-      serialized_response.empty()) {
-    error_callback_.Run(kNoResponseBodyError);
+  if (!source->GetResponseAsString(&serialized_response)) {
+    error_callback_.Run(kResponseBodyError);
     return;
   }
   result_callback_.Run(serialized_response);
 }
 
 void CryptAuthApiCallFlow::ProcessApiCallFailure(
     const net::URLFetcher* source) {
   std::string error_message;
   if (source->GetStatus().status() == net::URLRequestStatus::SUCCESS) {
     error_message =
         kHttpStatusErrorPrefix + base::IntToString(source->GetResponseCode());
   } else {
     error_message = kRequestFailedError;
   }
   error_callback_.Run(error_message);
 }
 
 }  // proximity_auth