InputReader: Notify policy of device changes after flushing events

...so that the rest of the listeners are synchonized with the device
changes (through NotifyInputDevicesChangedArgs) before the policy
can react to the changes.

Bug: 324061913
Bug: 293587049
Test: atest inputflinger_tests
Test: atest VirtualDeviceMirrorDisplayTest#virtualMouse_buttonEvent --rerun-until-failure
Change-Id: I818b1e688565d30867295019c5baae29cb5bdbf2

Author: prabirmsp

services/inputflinger/reader/InputReader.cpp

@@ -164,19 +164,6 @@ void InputReader::loopOnce() {
         std::swap(notifyArgs, mPendingArgs);
     } // release lock
 
-    // Send out a message that the describes the changed input devices.
-    if (inputDevicesChanged) {
-        mPolicy->notifyInputDevicesChanged(inputDevices);
-    }
-
-    // Notify the policy of the start of every new stylus gesture outside the lock.
-    for (const auto& args : notifyArgs) {
-        const auto* motionArgs = std::get_if<NotifyMotionArgs>(&args);
-        if (motionArgs != nullptr && isStylusPointerGestureStart(*motionArgs)) {
-            mPolicy->notifyStylusGestureStarted(motionArgs->deviceId, motionArgs->eventTime);
-        }
-    }
-
     // Flush queued events out to the listener.
     // This must happen outside of the lock because the listener could potentially call
     // back into the InputReader's methods, such as getScanCodeState, or become blocked
@@ -187,6 +174,21 @@ void InputReader::loopOnce() {
     for (const NotifyArgs& args : notifyArgs) {
         mNextListener.notify(args);
     }
+
+    // Notify the policy that input devices have changed.
+    // This must be done after flushing events down the listener chain to ensure that the rest of
+    // the listeners are synchronized with the changes before the policy reacts to them.
+    if (inputDevicesChanged) {
+        mPolicy->notifyInputDevicesChanged(inputDevices);
+    }
+
+    // Notify the policy of the start of every new stylus gesture.
+    for (const auto& args : notifyArgs) {
+        const auto* motionArgs = std::get_if<NotifyMotionArgs>(&args);
+        if (motionArgs != nullptr && isStylusPointerGestureStart(*motionArgs)) {
+            mPolicy->notifyStylusGestureStarted(motionArgs->deviceId, motionArgs->eventTime);
+        }
+    }
 }
 
 std::list<NotifyArgs> InputReader::processEventsLocked(const RawEvent* rawEvents, size_t count) {