Can you point out a keyboard app (or mode within such keyboard app) available on stock Android which makes use of getExtractedText()?  Chromium doesn't necessarily have a commitment to supporting every legacy feature of InputConnection, in fact we might prefer to continue ignoring those that have zero use (e.g. we don't not support most of the subclasses of text Spannables).  Also, if there is no manual test target, it makes it difficult to determine if whether or not have caused a regression in the code you're adding, therefore such code is also somewhat unmaintainable.

Note this bug was filed for patch https://codereview.chromium.org/2500663002/

Hi aelias@,
As we support a variant of the Chromium Browser, the Silk Browser on the Amazon FireOS platform; this change is geared toward consumption on the Amazon FireOS which is based on AOSP rather than Stock Android.

Furthermore FireOS does in fact use the legacy features of InputConnection which is why this change helps us support this particular use case.

Also we plan to have sufficient automated test coverage to detect regressions on the legacy InputConnection feature to help maintain the feature until it is deprecated or reaches End of Life.

Hmm, looks like we universally pass in IME_FLAG_NO_EXTRACT_UI flag to IME.  It means this is unlikely to be called, but the documentation doesn't specify this amounts to a contract that getExtractedText won't be called by IME, either.

So there is a (debatable) technical compliance reason to add this, but also, looking more closely at it, the support burden doesn't look too high and it does provide a nicely asynchronous way for IME to obtain text which we may prefer to encourage over the blocking synchronous getters.  So I guess we can take this, I added code review comments.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9b5ebac3230f3c90782296ae95396e7f512729bc

commit 9b5ebac3230f3c90782296ae95396e7f512729bc
Author: bhallam <bhallam@amazon.com>
Date: Wed May 10 05:42:09 2017

Relay Text Field Updates from ContentView to External InputMethodManager.

This change surfaces up all ExtractedText updates from the content view
back to the InputMethodManager.

Is is applicable to allow consumers of the Android InputManager
to receive text change events back.

This change does not affect Standard Input Method Managers such as the
Android Default Keyboard registered to the platform but specifically
affects External Input Method apps like virtual floating keyboard
implementations or screen keyboard overlay implementations.

In addition this change is consistent with the guidelines given as part of
https://developer.android.com/reference/android/view/inputmethod/InputConnection.html
States that if the GET_EXTRACTED_TEXT_MONITOR flag is set,
you should be calling updateExtractedText(View, int, ExtractedText)
whenever you call updateSelection(View, int, int, int, int).

BUG= 673819 
TEST=New ContentShellJunitTests, Existing ContentShell Instrumentation Tests.

Review-Url: https://codereview.chromium.org/2500663002
Cr-Commit-Position: refs/heads/master@{#470488}

[modify] https://crrev.com/9b5ebac3230f3c90782296ae95396e7f512729bc/content/public/android/java/src/org/chromium/content/browser/input/ImeAdapter.java
[modify] https://crrev.com/9b5ebac3230f3c90782296ae95396e7f512729bc/content/public/android/java/src/org/chromium/content/browser/input/InputMethodManagerWrapper.java
[modify] https://crrev.com/9b5ebac3230f3c90782296ae95396e7f512729bc/content/public/android/java/src/org/chromium/content/browser/input/ThreadedInputConnection.java
[modify] https://crrev.com/9b5ebac3230f3c90782296ae95396e7f512729bc/content/public/android/junit/src/org/chromium/content/browser/input/ThreadedInputConnectionTest.java