properly escape json names (#652)

src/json_reporter.cc

@@ -78,7 +78,12 @@ bool JSONReporter::ReportContext(const Context& context) {
   out << indent << FormatKV("date", walltime_value) << ",\n";
 
   if (Context::executable_name) {
-    out << indent << FormatKV("executable", Context::executable_name) << ",\n";
+    // windows uses backslash for its path separator,
+    // which must be escaped in JSON otherwise it blows up conforming JSON
+    // decoders
+    std::string executable_name = Context::executable_name;
+    ReplaceAll(&executable_name, "\\", "\\\\");
+    out << indent << FormatKV("executable", executable_name) << ",\n";
   }
 
   CPUInfo const& info = context.cpu_info;

test/reporter_output_test.cc

@@ -23,7 +23,8 @@ static int AddContextCases() {
            {{"^\\{", MR_Default},
             {"\"context\":", MR_Next},
             {"\"date\": \"", MR_Next},
-            {"\"executable\": \".*/reporter_output_test(\\.exe)?\",", MR_Next},
+            {"\"executable\": \".*(/|\\\\)reporter_output_test(\\.exe)?\",",
+             MR_Next},
             {"\"num_cpus\": %int,$", MR_Next},
             {"\"mhz_per_cpu\": %float,$", MR_Next},
             {"\"cpu_scaling_enabled\": ", MR_Next},