Fix trace_event code to accept double-quote and backslash characters in string values

base/debug/trace_event.cc

 // Copyright (c) 2011 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 "base/debug/trace_event.h"
 
 #include <algorithm>
 
 #if defined(OS_WIN)
 #include "base/debug/trace_event_win.h"
@@ skipping 69 matching lines @@
                      static_cast<unsigned long long>(
                        reinterpret_cast<intptr_t>(
                          as_pointer())));
       *out += temp_string;
       break;
     case TRACE_TYPE_STRING:
     case TRACE_TYPE_STATIC_STRING:
       *out += "\"";
       start_pos = out->size();
       *out += as_string() ? as_string() : "NULL";
-      // replace " character with '
-      while ((start_pos = out->find_first_of('\"', start_pos)) !=
-             std::string::npos)
-        (*out)[start_pos] = '\'';
+      // insert backslash before special characters for proper json format.
+      while ((start_pos = out->find_first_of("\\\"", start_pos)) !=
+             std::string::npos) {
+        out->insert(start_pos, 1, '\\');
+        // skip inserted escape character and following character.
+        start_pos += 2;
+      }
       *out += "\"";
       break;
     default:
       NOTREACHED() << "Don't know how to print this value";
       break;
   }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 //
@@ skipping 431 matching lines @@
         NULL, 0, NULL, 0,
         p_data_->threshold_begin_id, p_data_->threshold,
         TraceLog::EVENT_FLAG_NONE);
   }
 }
 
 } // namespace internal
 
 }  // namespace debug
 }  // namespace base