LibIPC: Only start responsiveness timer after sending client a message

Instead of always running the responsiveness timer for IPC clients,
we now only start it after sending a message. This avoids waking up
otherwise idle clients to do ping/pong busywork.

Libraries/LibIPC/ClientConnection.h

@@ -101,6 +101,7 @@ public:
     }
 
     virtual void may_have_become_unresponsive() {}
+    virtual void did_become_responsive() {}
 
     void post_message(const Message& message)
     {
@@ -130,6 +131,8 @@ public:
         }
 
         ASSERT(static_cast<size_t>(nwritten) == buffer.size());
+
+        m_responsiveness_timer->start();
     }
 
     void drain_messages_from_client()
@@ -156,8 +159,10 @@ public:
             bytes.append(buffer, nread);
         }
 
-        if (!bytes.is_empty())
+        if (!bytes.is_empty()) {
-            m_responsiveness_timer->restart();
+            m_responsiveness_timer->stop();
+            did_become_responsive();
+        }
 
         size_t decoded_bytes = 0;
         for (size_t index = 0; index < bytes.size(); index += decoded_bytes) {

Services/WindowServer/ClientConnection.cpp

@@ -844,4 +844,9 @@ void ClientConnection::may_have_become_unresponsive()
     });
 }
 
+void ClientConnection::did_become_responsive()
+{
+    set_unresponsive(false);
+}
+
 }

Services/WindowServer/ClientConnection.h

@@ -89,6 +89,7 @@ private:
     // ^ClientConnection
     virtual void die() override;
     virtual void may_have_become_unresponsive() override;
+    virtual void did_become_responsive() override;
 
     void set_unresponsive(bool);
     void destroy_window(Window&, Vector<i32>& destroyed_window_ids);