Move drag event to InputDispatcher (1/n)

This CL adds the ability to send a DRAG event through the
InputChannel, and adds the appropriate processing logic to
InputPublisher and InputConsumer.

Bug: 158242495
Test: atest libinput_tests InputPublisherAndConsumerTest
Change-Id: I7aead341a9851facf654024c476bd6d7eaae4590
diff --git a/libs/input/tests/StructLayout_test.cpp b/libs/input/tests/StructLayout_test.cpp
index 8f43608..3d80b38 100644
--- a/libs/input/tests/StructLayout_test.cpp
+++ b/libs/input/tests/StructLayout_test.cpp
@@ -87,6 +87,12 @@
   CHECK_OFFSET(InputMessage::Body::Capture, pointerCaptureEnabled, 4);
   CHECK_OFFSET(InputMessage::Body::Capture, empty, 5);
 
+  CHECK_OFFSET(InputMessage::Body::Drag, eventId, 0);
+  CHECK_OFFSET(InputMessage::Body::Drag, x, 4);
+  CHECK_OFFSET(InputMessage::Body::Drag, y, 8);
+  CHECK_OFFSET(InputMessage::Body::Drag, isExiting, 12);
+  CHECK_OFFSET(InputMessage::Body::Drag, empty, 13);
+
   CHECK_OFFSET(InputMessage::Body::Finished, handled, 0);
   CHECK_OFFSET(InputMessage::Body::Finished, empty, 1);
   CHECK_OFFSET(InputMessage::Body::Finished, consumeTime, 8);
@@ -110,6 +116,7 @@
     static_assert(sizeof(InputMessage::Body::Finished) == 16);
     static_assert(sizeof(InputMessage::Body::Focus) == 8);
     static_assert(sizeof(InputMessage::Body::Capture) == 8);
+    static_assert(sizeof(InputMessage::Body::Drag) == 16);
 }
 
 // --- VerifiedInputEvent ---