InputTransport: store fd in a unique_fd.

Use unique_fd to hold the file descriptor, so that it gets protected
from being closed by someone else by fdsan.

Test: atest libinput_tests inputflinger_tests
Change-Id: I08df199294f9ddd7646c7bcd637b9c035e3c1e12
diff --git a/libs/input/IInputFlinger.cpp b/libs/input/IInputFlinger.cpp
index d6a73bf..90f6e09 100644
--- a/libs/input/IInputFlinger.cpp
+++ b/libs/input/IInputFlinger.cpp
@@ -92,15 +92,13 @@
     }
     case REGISTER_INPUT_CHANNEL_TRANSACTION: {
         CHECK_INTERFACE(IInputFlinger, data, reply);
-        sp<InputChannel> channel = new InputChannel();
-        channel->read(data);
+        sp<InputChannel> channel = InputChannel::read(data);
         registerInputChannel(channel);
         break;
     }
     case UNREGISTER_INPUT_CHANNEL_TRANSACTION: {
         CHECK_INTERFACE(IInputFlinger, data, reply);
-        sp<InputChannel> channel = new InputChannel();
-        channel->read(data);
+        sp<InputChannel> channel = InputChannel::read(data);
         unregisterInputChannel(channel);
         break;
     }