adbd: Fix check against valid payload size

block->payload and its size are not valid when it is used to check
against bytes_left due to std::move() performed on its just prior
to the check. Hence check will always fail to detect the case where
received data is more than expected. To detect this condition and
allow error handling with std::move(), remove extra payload variable
and directly use block->payload.

Bug: http://b/168917244
Change-Id: I992bbba9d9a9861a195834f69d62e69b90658210

adb/daemon/usb.cpp

@@ -584,12 +584,11 @@ struct UsbFfsConnection : public Connection {
                 incoming_header_ = msg;
             } else {
                 size_t bytes_left = incoming_header_->data_length - incoming_payload_.size();
-                Block payload = std::move(block->payload);
                 if (block->payload.size() > bytes_left) {
                     HandleError("received too many bytes while waiting for payload");
                     return false;
                 }
-                incoming_payload_.append(std::move(payload));
+                incoming_payload_.append(std::move(block->payload));
             }
 
             if (incoming_header_->data_length == incoming_payload_.size()) {