Add warning to ApplicationStatus about usage

Adds a warning that ApplicationStatus may not work properly in WebView
or WebLayer, and that it is intended to be moved out of //base. While
this is enforced by DEPS (at least in //components), that isn't as
discoverable until the end of prepping a patch. This adds a class-level
comment to provide better visibility to warning users off of using this
if they are trying to break other //chrome dependencies.

Bug: 470582
Change-Id: I3593a44b1075b51ab99a114074b8a54c80e916f8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2461333
Commit-Queue: Alexander Cooper <alcooper@chromium.org>
Commit-Queue: Richard Coles <torne@chromium.org>
Auto-Submit: Alexander Cooper <alcooper@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815252}

base/android/java/src/org/chromium/base/ApplicationStatus.java

@@ -36,6 +36,8 @@ import javax.annotation.concurrent.GuardedBy;
 /**
  * Provides information about the current activity's status, and a way
  * to register / unregister listeners for state changes.
+ * TODO(https://crbug.com/470582): ApplicationStatus will not work on WebView/WebLayer, and
+ * should be moved out of base and into //chrome. It should not be relied upon for //components.
  */
 @JNINamespace("base::android")
 public class ApplicationStatus {