Task-queue should only apply "runnable" concept to tasks

[gterzian]

When a pipeline is not "fully-active", the task-queue stores messages until the pipeline because "fully-active" again. The filtering is done at

servo/components/script/task_queue.rs

Line 142 in d553158

self.store_task_for_inactive_pipeline(msg, &pipeline_id);

This is meant to implement the concept of runnable, which is how an event-loop selects tasks to run.

So, this concept only applies to tasks, yet the task-queue currently applies it to a T messages, which in practice is a message ultimately containing a script_runtime::CommonScriptMsg, and not all of these are tasks.

So we should only apply the "runnable" test to tasks, not all T, and the way to find out whether T contains a task, is by applying the same check the task-queue already applies in it's related "throttling" logic, by calling T::task_source_name

servo/components/script/task_queue.rs

Line 123 in d553158

let task_source = match msg.task_source_name() {

If T doesn't have a task-source name, it's not a task, and it should always run whether it's associated document is fully-active or not.

[gterzian]

Actually, that's not true.

The runnable check is only applied to tasks, because it's only applied to messages that have a pipeline_id:

servo/components/script/task_queue.rs

Line 140 in d553158

if let Some(pipeline_id) = msg.pipeline_id() {

If you look at the various implementations of QueuedTaskConversion, pipeline_id returns None if the message doesn't contain a task:

servo/components/script/script_thread.rs

Line 306 in 901fef5

fn pipeline_id(&self) -> Option<PipelineId> {

servo/components/script/dom/serviceworkerglobalscope.rs

Line 75 in a905916

fn pipeline_id(&self) -> Option<PipelineId> {

servo/components/script/dom/dedicatedworkerglobalscope.rs

Line 117 in 147c042

fn pipeline_id(&self) -> Option<PipelineId> {

[gterzian]

If anything, this requires a comment, since it fooled the author of the actual code for a while, that makes clear that the pipeline_id call includes a check on whether the message is a task or not.

servo/components/script/task_queue.rs

Line 140 in d553158

if let Some(pipeline_id) = msg.pipeline_id() {