Hook up PA_LOG() logs to chrome://proximity-auth WebUI.

components/proximity_auth/webui/proximity_auth_webui_handler.cc

 // Copyright 2015 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/webui/proximity_auth_webui_handler.h"
 
+#include "base/bind.h"
+#include "base/i18n/time_formatting.h"
+#include "base/values.h"
+#include "content/public/browser/web_ui.h"
+
 namespace proximity_auth {
 
+namespace {
+
+// Keys in the JSON representation of a log message.
+const char kLogMessageTextKey[] = "text";
+const char kLogMessageTimeKey[] = "time";
+const char kLogMessageFileKey[] = "file";
+const char kLogMessageLineKey[] = "line";
+const char kLogMessageSeverityKey[] = "severity";
+
+// Converts |log_message| to a raw dictionary value used as a JSON argument to
+// JavaScript functions.
+scoped_ptr<base::DictionaryValue> LogMessageToDictionary(
+    const LogBuffer::LogMessage& log_message) {
+  base::DictionaryValue* dictionary = new base::DictionaryValue();

[Ilya Sherman, 2015/05/13 21:57:10]

nit: Please use a scoped_ptr here, and .Pass() it below.

[Tim Song, 2015/05/13 23:26:55]

Done.

+  dictionary->SetString(kLogMessageTextKey, log_message.text);
+  dictionary->SetString(kLogMessageTimeKey,
+                        base::TimeFormatTimeOfDay(log_message.time));
+  dictionary->SetString(kLogMessageFileKey, log_message.file);
+  dictionary->SetInteger(kLogMessageLineKey, log_message.line);
+  dictionary->SetInteger(kLogMessageSeverityKey,
+                         static_cast<int>(log_message.severity));
+  return make_scoped_ptr(dictionary);
+}
+
+}  // namespace
+
 ProximityAuthWebUIHandler::ProximityAuthWebUIHandler() {
+  LogBuffer::GetInstance()->AddObserver(this);
 }
 
 ProximityAuthWebUIHandler::~ProximityAuthWebUIHandler() {
+  LogBuffer::GetInstance()->RemoveObserver(this);
 }
 
 void ProximityAuthWebUIHandler::RegisterMessages() {
+  web_ui()->RegisterMessageCallback(
+      "clearLogBuffer", base::Bind(&ProximityAuthWebUIHandler::ClearLogBuffer,
+                                   base::Unretained(this)));
+
+  web_ui()->RegisterMessageCallback(
+      "getLogMessages", base::Bind(&ProximityAuthWebUIHandler::GetLogMessages,
+                                   base::Unretained(this)));
+}
+
+void ProximityAuthWebUIHandler::OnLogMessageAdded(
+    const LogBuffer::LogMessage& log_message) {
+  scoped_ptr<base::DictionaryValue> dictionary(
+      LogMessageToDictionary(log_message).release());

[Ilya Sherman, 2015/05/13 21:57:10]

nit: You should be able to just assign the value, or maybe call .Pass() if that
doesn't work.  .release() is dispreferred where more clearly safe options work.

[Tim Song, 2015/05/13 23:26:55]

I tried both and got compile errors. It seems scoped_ptr instances don't cast to
their pointer values in this case.

[Ilya Sherman, 2015/05/13 23:42:34]

Hmm, according to [
https://code.google.com/p/chromium/codesearch#chromium/src/base/memory/scoped...
], either of the following should work:

scoped_ptr<base::DictionaryValue> dictionary =
LogMessageToDictionary(log_message);
scoped_ptr<base::DictionaryValue>
dictionary(LogMessageToDictionary(log_message).Pass());

You tried both and got compile errors?  I'm pretty surprised by that, especially
since I'm pretty sure I've seen this pattern used elsewhere in the code.

[Tim Song, 2015/05/14 03:12:03]

Sorry, my bad. I thought this comment was referring to the other release() call
below.

+  web_ui()->CallJavascriptFunction("LogBufferInterface.onLogMessageAdded",
+                                   *dictionary);
+}
+
+void ProximityAuthWebUIHandler::OnLogBufferCleared() {
+  web_ui()->CallJavascriptFunction("LogBufferInterface.onLogBufferCleared");
+}
+
+void ProximityAuthWebUIHandler::GetLogMessages(const base::ListValue* args) {
+  base::ListValue json_logs;
+  auto logs = LogBuffer::GetInstance()->logs();
+  std::transform(logs->begin(), logs->end(), json_logs.begin(),
+                 [](const LogBuffer::LogMessage& log) {
+                   return LogMessageToDictionary(log).release();
+                 });
+
+  web_ui()->CallJavascriptFunction("LogBufferInterface.onGotLogMessages",
+                                   json_logs);
+}
+
+void ProximityAuthWebUIHandler::ClearLogBuffer(const base::ListValue* args) {
+  // The OnLogBufferCleared() observer function will be called after the buffer
+  // is cleared.
+  LogBuffer::GetInstance()->Clear();
 }
 
 }  // namespace proximity_auth