Avoid heap allocations in IPAddress

chrome/browser/media/webrtc/webrtc_text_log_handler.cc

 // Copyright 2016 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 "chrome/browser/media/webrtc/webrtc_text_log_handler.h"
 
 #include <map>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/bind.h"
+#include "base/containers/stack_container.h"
 #include "base/cpu.h"
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
 #include "base/sys_info.h"
 #include "base/time/time.h"
 #include "chrome/browser/media/webrtc/webrtc_log_uploader.h"
 #include "chrome/common/channel_info.h"
 #include "chrome/common/media/webrtc_logging_messages.h"
 #include "components/version_info/version_info.h"
@@ skipping 47 matching lines @@
       size_t find_pos = sensitive_address.rfind('.');
       if (find_pos == std::string::npos)
         return std::string();
       sensitive_address.resize(find_pos);
       sensitive_address += ".x";
       break;
     }
     case net::IPAddress::kIPv6AddressSize: {
       // TODO(grunell): Create a string of format "1:2:3:x:x:x:x:x" to clarify
       // that the end has been stripped out.
-      std::vector<uint8_t> bytes = address.bytes();
-      std::fill(bytes.begin() + 6, bytes.end(), 0);
-      net::IPAddress stripped_address(bytes);
+      base::StackVector<uint8_t, 16> bytes;

[eroman, 2017/05/19 22:00:07]

How about without StackVector:

net::IPAddressBytes stripped = address.bytes();
std::fill(stripped.begin() + 6, stripped.end(), 0);
sensitive_address = net::IPAddress(stripped).ToString();

(The awkwardness of that last line suggests merging net::IPAddress /
net::IPAddressBytes, or making IPAddress methods free-floating functions).

[Ryan Hamilton, 2017/05/20 03:21:44]

Done. (With minor modifications)
This seems like a fine idea, do you want that to happen now, or would a TODO
suffice?

[eroman, 2017/05/22 18:06:44]

Let's worry about that later (Was just an observation). Thanks for asking
though!

+      for (uint8_t byte : address.bytes())
+        bytes->push_back(byte);
+      std::fill(bytes->begin() + 6, bytes->end(), 0);
+      net::IPAddress stripped_address(bytes->data(), bytes->size());
       sensitive_address = stripped_address.ToString();
       break;
     }
     default: { break; }
   }
   return sensitive_address;
 #else
   return address.ToString();
 #endif
 }
@@ skipping 412 matching lines @@
   }
 }
 
 void WebRtcTextLogHandler::DisableBrowserProcessLoggingOnUIThread() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   content::RenderProcessHost* host =
       content::RenderProcessHost::FromID(render_process_id_);
   if (host)
     host->ClearWebRtcLogMessageCallback();
 }