Make Sky's EditableText mostly work

Make Sky's EditableText mostly work

This CL factors EditableString out of EditableText and implements more of the
InputConnection functions. As a result, EditableText now basically works.

This CL also paves the way to make EditableText stateless by using
EditableString as its state object. However, there's still a bit more work to
do to make that a reality (e.g., factoring out the cursor blink timer and the
connection to the keyboard).

R=eseidel@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/507c02194dcb93c738f4fd33d1889fb4d955cd5d

[eseidel, 2015-03-10 18:39:29]

lgtm

https://codereview.chromium.org/995073002/diff/60001/sky/examples/editor/edit...
File sky/examples/editor/editable_string.dart (right):

https://codereview.chromium.org/995073002/diff/60001/sky/examples/editor/edit...
sky/examples/editor/editable_string.dart:57: text += newText;
You should make this more self-documenting.

[abarth-chromium, 2015-03-10 19:32:00]

Committed patchset #4 (id:60001) manually as
507c02194dcb93c738f4fd33d1889fb4d955cd5d (presubmit successful).