This reverts commit 0d5f2e901d1953d04eb45004666d34a4537a0060.
Due to merge conflicts, this also reverts #22275:
Revert "Do not involve external_view_embedder in submit frame process if threads are not merged. (#22275)"
This reverts commit 016fbde1bb275288242e2cf097b52af1dd66ab06.
This (mostly) re-lands #21163, which was reverted in #22321
This switches from using onKeyDown to using dispatchKeyEvent on Android so that keys can be intercepted handled by the framework and not continue to be dispatched to other controls.
It also now intercepts key events sent to InputConnection.sendKeyEvent, as some IMEs do (e.g. the Hacker's Keyboard), and sends them to Flutter.
This fixes the problem where (for example) pressing TAB on a hardware keyboard sends the tab to both the text field and to the focus traversal system.
Note that we still can't intercept all keystrokes given to a soft keyboard, only those which the soft keyboard decides to send to InputConnection.sendKeyEvent, and system keys (like the back button) are only received if the IME doesn't eat them.
This re-lands #21163, which was reverted in #22004
Now that flutter/flutter#67359 has landed, this change will no longer cause spaces (and other shortcuts) to be ignored in text fields if there is no action associated with the intent, even if there is a shortcut key mapping to an intent.
It also no longer causes web test failures (as far as I can tell without submitting it: the same tests don't fail locally).
Here's the original PR description:
This switches from using dispatchKeyEvent to using dispatchKeyEventPreIme so that keys can be intercepted before they reach the IME and be handled by the framework.
It also now intercepts key events sent to InputConnection.sendKeyEvent, as some IMEs do (e.g. the Hacker's Keyboard), and sends the to Flutter before sending them to the IME (which it now only does if they are not handled by the framework).
This fixes the problem where pressing TAB on a hardware keyboard sends the tab to both the text field and to the focus traversal system.
Note that we still can't intercept all keystrokes given to a soft keyboard, only those which the soft keyboard decides to send to InputConnection.sendKeyEvent.
Switches the Linux embedding from the standard C API to the new proctable version, to allow for unit testing of the embedding layer separately from the embedder APIs implementation.
