Add FocusEvent and InputMessage::Type::FOCUS

FocusEvents will be consumed by InputConsumer on the app side. They
will be used to notify app that focus has been gained / lost. They will
also carry information about the current state of touch mode.

Also add a new type of InputMessage with type FOCUS.
This new data structure will be used to pass focus events to the apps
from input across the socket.

Bug: 70668286
Test: presubmit
Change-Id: I88582c64ee41ecb49623b9b7f5c149eafa694788
diff --git a/libs/input/tests/StructLayout_test.cpp b/libs/input/tests/StructLayout_test.cpp
index 0fb6cfc..9ab0dba 100644
--- a/libs/input/tests/StructLayout_test.cpp
+++ b/libs/input/tests/StructLayout_test.cpp
@@ -69,6 +69,10 @@
   CHECK_OFFSET(InputMessage::Body::Motion, pointerCount, 88);
   CHECK_OFFSET(InputMessage::Body::Motion, pointers, 96);
 
+  CHECK_OFFSET(InputMessage::Body::Focus, seq, 0);
+  CHECK_OFFSET(InputMessage::Body::Focus, hasFocus, 4);
+  CHECK_OFFSET(InputMessage::Body::Focus, inTouchMode, 6);
+
   CHECK_OFFSET(InputMessage::Body::Finished, seq, 0);
   CHECK_OFFSET(InputMessage::Body::Finished, handled, 4);
 }
@@ -87,6 +91,7 @@
                   offsetof(InputMessage::Body::Motion, pointers) +
                           sizeof(InputMessage::Body::Motion::Pointer) * MAX_POINTERS);
     static_assert(sizeof(InputMessage::Body::Finished) == 8);
+    static_assert(sizeof(InputMessage::Body::Focus) == 8);
 }
 
 } // namespace android