Naively embedded platform views on Android were never able to receive
keyboard input, because they were never focusable. So far we've worked
around the limiation by hooking into InputMethodManager and proxying the
InputConnection from a focused window over to the embeded view.
Android Q changed InputMethodManager to be instanced per display instead
of a singleton. Because of this our proxy hook was never being called,
since it was being set up on a different instance of IMM than was being
used in the virtual display.
Update `SingleViewPresentation` to store the IMM from the focused window
and return it whenever there are any calls to `INPUT_METHOD_SERVICE`.
This hooks our proxy back into place for the embedded view in the
virtual display. This restores the functionality of our workaround from
previous versions.
Unfortunately there's still a lot of noisy error logs from IMM here. It
can tell that the IMM has a different displayId than what it's expecting
from the window.
This also updates the unit tests to support SDK=27. SDK 16 doesn't have
DisplayManager, so there were NPEs attempting to instantiate the class
under test.
`gclient sync` now grabs Robolectric, JUnit, and their transitive
runtime dependencies. They're being stored in a new CIPD package,
`flutter/android/robolectric_bundle`.
`shell/platform/android/BUILD.gn` has a new target for building the
tests, `robolectric_tests`. `testing/run_tests.py` has been extended to
build and run the new target. Runs the android tests under
"build_and_test_android" on CI.
This also adds some very simple sample tests to start with and a README
to the java tests directory.
