message: Log device placement to available log listeners in session mode
  This is needed to have device placement logging work in colab for code that runs TensorFlow in session mode.
diff: @@ -42,6 +42,7 @@ limitations under the License.
  #include "tensorflow/core/framework/graph.pb.h"
  #include "tensorflow/core/framework/graph_def_util.h"
  #include "tensorflow/core/framework/log_memory.h"
  +#include "tensorflow/core/framework/logging.h"
  #include "tensorflow/core/framework/node_def.pb.h"
  #include "tensorflow/core/framework/run_handler.h"
  #include "tensorflow/core/framework/tensor.h"
  @@ -353,7 +354,10 @@ DirectSession::DirectSession(const SessionOptions& options,
  } else {
  printf("Device mapping:\n%s", mapping_str.c_str());
  }
  - LOG(INFO) << "Device mapping:\n" << mapping_str;
  + string msg = strings::StrCat("Device mapping:\n", mapping_str);
  + if (!logging::LogToListeners(msg)) {
  + LOG(INFO) << msg;
  + }
  }
  for (auto d : device_mgr_->ListDevices()) {
  devices_.push_back(d);
  