This patch wires Mozart's text input system to flutter/textinput. This patch
doesn't fully work yet because the Mozart side isn't fully implemented.

Disable info debug messages from the layers to cut down log spam.

* Update Skia revision to 7120b2d577d3aab1f51c5af1530a68c57ca51696.
* Update licenses.
* Account for content handler updates.

Fixes build.

Fixes https://github.com/flutter/flutter/issues/6774

This change brings iOS return key behaviour in line with current behaviour on
Android.

* Implements TextInputClient.performAction for iOS Adds FlutterTextInputAction
* enum Defaults return key to 'Done' Ends editing and hides the keyboard if
* 'Done' is pressed

Future work is planned to support configurable return/action key behaviour.
See: #9573, #9210, #8028.

We now wait for 1 second for the display driver to appear on Fuchsia. This
approach is a stopgap until Vulkan is required for graphics.

Previously, the last error was a global static. Now it is a thread-specific
value, which means we need to visit the UI thread to read the value.

It controls whether the observatory and diagnostic server will
bind to the IPv6 loopback address rather than the IPv4.

Fixes https://github.com/flutter/flutter/issues/9813

Previously, it was a static. Doesn't have much effect in practice because we
only use this microtask queue for main isolates, which exist on a single
thread.

We are removing some indirect includes from SkCanvas.h.

Updating clients to pull required headers explicitly.

When pasting an item of type kTextPlainFormat from the pasteboard, ensure there actually is a string in the pasteboard. (#3638)

See https://github.com/flutter/flutter/issues/7626

Instead of updating to match new HID touchscreen hacks exposed by
magenta, just remove the direct input layer entirely.  Mozart all the
time from now on.