gpu: Maintain the deferred log messages separately from the IPC messages.

Instead of keeping a queue of IPC messages in GpuChildThread for the
deferred log messages that are sent to the browser, maintain a queue of
structs describing the log messages. This makes it easier to follow the
code, and easier to replace the chrome IPC with mojo IPC in subsequent
patches.

BUG=643746

Review-Url: https://codereview.chromium.org/2599203003
Cr-Commit-Position: refs/heads/master@{#441318}

content/gpu/gpu_child_thread.cc

@@ -187,10 +187,6 @@ GpuChildThread::GpuChildThread(
 }
 
 GpuChildThread::~GpuChildThread() {
-  while (!deferred_messages_.empty()) {
-    delete deferred_messages_.front();
-    deferred_messages_.pop();
-  }
 }
 
 void GpuChildThread::Shutdown() {
@@ -320,7 +316,8 @@ void GpuChildThread::OnInitialize(const gpu::GpuPreferences& gpu_preferences) {
   gpu_info_.initialization_time = base::Time::Now() - process_start_time_;
   Send(new GpuHostMsg_Initialized(!dead_on_arrival_, gpu_info_));
   while (!deferred_messages_.empty()) {
-    Send(deferred_messages_.front());
+    const LogMessage& log = deferred_messages_.front();
+    Send(new GpuHostMsg_OnLogMessage(log.severity, log.header, log.message));
     deferred_messages_.pop();
   }
 

content/gpu/gpu_child_thread.h

@@ -56,7 +56,12 @@ class GpuChildThread : public ChildThreadImpl,
                        public gpu::GpuChannelManagerDelegate,
                        public base::FieldTrialList::Observer {
  public:
-  typedef std::queue<IPC::Message*> DeferredMessages;
+  struct LogMessage {
+    int severity;
+    std::string header;
+    std::string message;
+  };
+  typedef std::queue<LogMessage> DeferredMessages;
 
   GpuChildThread(std::unique_ptr<gpu::GpuWatchdogThread> gpu_watchdog_thread,
                  bool dead_on_arrival,

content/gpu/gpu_main.cc

@@ -106,10 +106,11 @@ bool GpuProcessLogMessageHandler(int severity,
                                  const char* file, int line,
                                  size_t message_start,
                                  const std::string& str) {
-  std::string header = str.substr(0, message_start);
-  std::string message = str.substr(message_start);
-  deferred_messages.Get().push(
-      new GpuHostMsg_OnLogMessage(severity, header, message));
+  GpuChildThread::LogMessage log;
+  log.severity = severity;
+  log.header = str.substr(0, message_start);
+  log.message = str.substr(message_start);
+  deferred_messages.Get().push(std::move(log));
   return false;
 }