message: Add device type to op profile.
diff: @@ -12,6 +12,8 @@ message Profile {
  Node by_category = 1;
  // Root of a profile broken down by program.
  Node by_program = 4;
  + // Device type.
  + string device_type = 5;
  }
  // An entry in the profile tree. (An instruction, or set of instructions).
  @@ -29,8 +31,7 @@ message Node {
  int32 num_children = 6; // Total number of children before pruning.
  // A category of XLA instructions.
  // name is a descriptive string, like "data formatting".
  - message InstructionCategory {
  - }
  + message InstructionCategory {}
  // A single XLA instruction.
  // name is the unique instruction id, like "%multiply.5".
  message XLAInstruction {
  