Are you doing this now? I was just working on a change.

I haven't started yet, assigning to you Paul. :)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9037d3eeb2ef0f33010f5c37cb5f7908437bdce4

commit 9037d3eeb2ef0f33010f5c37cb5f7908437bdce4
Author: Paul Miller <paulmiller@google.com>
Date: Fri Sep 22 21:23:48 2017

WebView: Fix brittle reference to TextClassifier on pre-O

When a relevant WebView API is called, the TextClassifier plumbed
through the following layers, in order:

- WebViewChromium
- AwContents
- ContentViewCore
- SelectionPopupController
- SmartSelectionClient (implements SelectionClient)
- SmartSelectionProvider

by the following functions:

- setTextClassifier()
- getTextClassifier()
- getCustomTextClassifier()

While most of these functions only run on >= O,
AwContents.setNewAwContents() runs on < O, and calls setTextClassifier()
and getCustomTextClassifier(). This works on < O because the
TextClassifier is null, but the JVM may still attempt to load the class
under surprising circumstances, such as casting a null Object to a
TextClassifier.

Ensure setNewAwContents() doesn't call those on < O, and add some
assertions to make it more obvious that certain codepaths should only
happen on >= O.

BUG= 767641 

Change-Id: I6525936ca51ca758d9447500115700db32b4be7c
Reviewed-on: https://chromium-review.googlesource.com/679286
Reviewed-by: Bo <boliu@chromium.org>
Commit-Queue: Paul Miller <paulmiller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#503858}
[modify] https://crrev.com/9037d3eeb2ef0f33010f5c37cb5f7908437bdce4/android_webview/java/src/org/chromium/android_webview/AwContents.java
[modify] https://crrev.com/9037d3eeb2ef0f33010f5c37cb5f7908437bdce4/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
[modify] https://crrev.com/9037d3eeb2ef0f33010f5c37cb5f7908437bdce4/content/public/android/java/src/org/chromium/content/browser/SmartSelectionClient.java

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/79ec628c655e29592957b70fcd76882aa2b1269e

commit 79ec628c655e29592957b70fcd76882aa2b1269e
Author: Paul Miller <paulmiller@google.com>
Date: Sat Sep 23 00:50:20 2017

WebView: Assert >= O in AwAutofillProvider

to help avoid confusion, along the lines of
9037d3eeb2ef0f33010f5c37cb5f7908437bdce4.

BUG= 767641 

Change-Id: I2ebef3380cf3bcc517201b73cf6ca8a7e613f08b
Reviewed-on: https://chromium-review.googlesource.com/679815
Reviewed-by: Bo <boliu@chromium.org>
Commit-Queue: Paul Miller <paulmiller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#503922}
[modify] https://crrev.com/79ec628c655e29592957b70fcd76882aa2b1269e/android_webview/java/src/org/chromium/android_webview/AwAutofillProvider.java