Implement pointerDown and pointerUp webdriver actions
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Implement GetElementProperty wd command
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There are a few canvas2d-related dependencies that haven't updated, but they
only use euclid internally so that's not blocking landing the rest of the
changes.
Given the size of this patch, I think it's useful to get this landed as-is.
Clean-up navigation
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1. Navigation as a result of following a hyperlink should be done in a task: https://html.spec.whatwg.org/multipage/links.html#following-hyperlinks:dom-manipulation-task-source
2. The javascript url navigation should also be done in a task: https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigating-across-documents:dom-manipulation-task-source
3. In `window.load_url`, it seems there is no need to send a message to the script-thread(the entirety of `load_url` should instead be done in a task when appropriate), so we can just do that last part "sync" by calling a method on the script, which will send a message to the constellation(for the parallel navigation steps), or queue task(for the JS navigation), as appropriate.
4. Separate the "normal" navigation flow from the handling of "navigate an iframe" message from constellation, since doing everything in one method as was previously done with `handle_navigate`, is confusing.
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security: check target and source origin before executing JS url
implement replacement-enabled flag as a HistoryEntryReplacement enum
add source origin string on loaddata
add LoadOrigin
iframe: remove optional load-data
auxiliaries: add load-data into info
constellation: remove url from Pipeline::new
check load origin: link to whatwg issue
switch loadorigin toplevel to constellation
Implement SwitchToWindow and DismissAlert WebDriver commands
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Implement Status WebDriver command
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add webdriver command "Find elements from Element"
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Forward WebDriver CompositionEvent
Dispatch composition events in JS.
Insert characters from composition events to text input.
CompositionEvents currently can only be
created by WebDriver and not by embedders.
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Dispatch composition events in JS.
Insert characters from composition events to text input.
CompositionEvents currently can only be
created by WebDriver and not by embedders.
