Extend AnrController to improve ANR dialog controls

I5431d22bd8faa75e3deab1960a2f721784f98d42 introduced a basic ANR
controller interface to allow services within the system_server
register to delay the ANR dialog during an ANR.

Some limitations of that interface were:
1. No way to cancel the ANR dialog if the normal function of the app
resumed during the delay
2. The AnrController#getAnrDelay method was serving a dual purpose of
returning the delay and showing an interim UI
3. The interim UI might live within an updatable mainline
module, hence forcing the system_server to block (asynchronously) on
the 'getter' for the binder call.

This cl addresses the problems above with the following new
methods on AnrController: onAnrDelayStarted and onAnrDelayCompleted.

These methods provide a clearer interface for the following reasons:
1. onAnrDelayCompleted will return a boolean value to indicate whether
the ANR dialog should still be shown after the delay
2. onAnrDelayStarted is a more explicit API that can be called
asynchronously without blocking to notify external components to show
an interim UI
3. The existing getAnrDelay can be handled completely within the
system_server without blocking on an external binder call

See design (2a) in go/transcoding-anrs for more details

Test: Manual
Bug: 170486601
Change-Id: Idb9190a0e6014ce64bf1412c26f6ae03f97e922d

1 files changed, 23 insertions, 1 deletions

diff --git a/core/java/android/app/AnrController.java b/core/java/android/app/AnrController.java
index cfc9d2715720..a0d4b3a6a753 100644
--- a/core/java/android/app/AnrController.java
+++ b/core/java/android/app/AnrController.java
@@ -23,7 +23,29 @@ package android.app;
 public interface AnrController {
     /**
      * Returns the delay in milliseconds for an ANR dialog that is about to be shown for
-     * {@code packageName}.
+     * {@code packageName} with {@code uid}.
+     *
+     * Implementations should only return a positive value if they actually expect the
+     * {@code packageName} to be delayed due to them.
+
+     * If there are multiple controllers registered, the controller with the max delay will
+     * be selected and will receive an {@link #onAnrDelayStarted} callback at the start of the
+     * delay and an {@link #onAnrDelayCompleted} at the end of the delay.
      */
     long getAnrDelayMillis(String packageName, int uid);
+
+    /**
+     * Notifies the controller at the start of the ANR dialog delay for {@code packageName} with
+     * {@code uid}. The controller can decide to show a progress UI after this notification.
+     */
+    void onAnrDelayStarted(String packageName, int uid);
+
+    /**
+     * Notifies the controller at the end of the ANR dialog delay for {@code packageName} with
+     * {@code uid}.
+     *
+     * @return whether the ANR dialog should be shown or cancelled. {@code true} if the
+     * ANR dialog should be shown, {@code false} if it should be cancelled.
+     */
+    boolean onAnrDelayCompleted(String packageName, int uid);
 }