Cast channel: Add cast.channel.getLogs extension API.

extensions/browser/api/cast_channel/cast_channel_api.cc

 // Copyright 2014 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 "extensions/browser/api/cast_channel/cast_channel_api.h"
 
 #include <limits>
 #include <string>
 
 #include "base/json/json_writer.h"
@@ skipping 435 matching lines @@
                        cast_channel::CHANNEL_ERROR_SOCKET_ERROR);
   } else {
     SetResultFromSocket(*socket);
     // This will delete |socket|.
     RemoveSocket(channel_id);
     socket = NULL;
   }
   AsyncWorkCompleted();
 }
 
+CastChannelGetLogsFunction::CastChannelGetLogsFunction() {
+}
+
+CastChannelGetLogsFunction::~CastChannelGetLogsFunction() {
+}
+
+bool CastChannelGetLogsFunction::PrePrepare() {
+  api_ = CastChannelAPI::Get(browser_context());
+  return CastChannelAsyncApiFunction::PrePrepare();
+}
+
+bool CastChannelGetLogsFunction::Prepare() {
+  return true;
+}
+
+void CastChannelGetLogsFunction::AsyncWorkStart() {
+  DCHECK(api_);
+
+  std::string log;
+  if (api_->GetLogger()->LogToString(&log)) {

[mark a. foltz, 2014/08/11 23:01:43]

How about having a LogToValue() method that can have the value take ownership of
the buffer, avoiding a copy?

[imcheng, 2014/08/12 07:42:09]

Yes, that's possible by asking zlib for the compressed upper bound size, then
Logger can allocate that buffer,  populate it, and return it. Done here.

+    base::BinaryValue* result =
+        base::BinaryValue::CreateWithCopiedBuffer(&log[0], log.size());

[mark a. foltz, 2014/08/11 23:01:43]

log.data()

[imcheng, 2014/08/12 07:42:09]

Done.

+    SetResult(result);
+  } else {
+    SetResult(new base::BinaryValue());

[mark a. foltz, 2014/08/11 23:01:43]

Does this mean no events were logged?  Or is this how an error is signaled?

[imcheng, 2014/08/12 07:42:09]

If no events is logged then a blob representing an empty Log proto will be
returned. This branch means something failed while getting logs (e.g.
serialization failed, compression failed, or some other reason). But I changed
it to SetError() instead.

+  }
+
+  api_->GetLogger()->Reset();
+
+  AsyncWorkCompleted();
+}
+
 }  // namespace extensions