Remove Webdriver Server's access to Constellation (#38212)

`WebDriverCommandMsg::TakeScreenshot` was the last thing blocking us
from removing constellation access in webdriver server. Now we can
happily remove it.

Surprisingly, this reduces binary size by 185KB for release profile in
Windows. #37737 removes a net total of 300 lines, but only reduced 98KB.

Testing: No regression after testing.

Signed-off-by: Euclid Ye <euclid.ye@huawei.com>

components/compositing/tracing.rs

@@ -34,7 +34,6 @@ mod from_constellation {
                 Self::CreateOrUpdateWebView(..) => target!("CreateOrUpdateWebView"),
                 Self::RemoveWebView(..) => target!("RemoveWebView"),
                 Self::TouchEventProcessed(..) => target!("TouchEventProcessed"),
-                Self::CreatePng(..) => target!("CreatePng"),
                 Self::IsReadyToSaveImageReply(..) => target!("IsReadyToSaveImageReply"),
                 Self::SetThrottled(..) => target!("SetThrottled"),
                 Self::NewWebRenderFrameReady(..) => target!("NewWebRenderFrameReady"),