docs: Don't be vague about where GTask dispatches the result

https://bugzilla.gnome.org/show_bug.cgi?id=783825

gio/gtask.c

@@ -47,11 +47,13 @@
  * Eventually, you will call a method such as
  * g_task_return_pointer() or g_task_return_error(), which will
  * save the value you give it and then invoke the task's callback
- * function (waiting until the next iteration of the main
+ * function in the
- * loop first, if necessary). The caller will pass the #GTask back
+ * [thread-default main context][g-main-context-push-thread-default]
- * to the operation's finish function (as a #GAsyncResult), and
+ * where it was created (waiting until the next iteration of the main
- * you can use g_task_propagate_pointer() or the like to extract
+ * loop first, if necessary). The caller will pass the #GTask back to
- * the return value.
+ * the operation's finish function (as a #GAsyncResult), and you can
+ * can use g_task_propagate_pointer() or the like to extract the
+ * return value.
  *
  * Here is an example for using GTask as a GAsyncResult:
  * |[<!-- language="C" -->
@@ -290,9 +292,10 @@
  * ## Asynchronous operations from synchronous ones
  *
  * You can use g_task_run_in_thread() to turn a synchronous
- * operation into an asynchronous one, by running it in a thread
+ * operation into an asynchronous one, by running it in a thread.
- * which will then dispatch the result back to the caller's
+ * When it completes, the result will be dispatched to the
- * #GMainContext when it completes.
+ * [thread-default main context][g-main-context-push-thread-default]
+ * where the #GTask was created.
  *
  * Running a task in a thread:
  *   |[<!-- language="C" -->