Replace redundant error code with a specific one

As discussed on b/163039465#comment3, it's not desirable to have two
distinct catch-all error bucket, where the difference is very subtle.

Opting to use STAGED_SESSION_CONFLICT which is more specific, but not
too specific. We can use this error is any scenarios where a staged
session interferes with installation of another staged session and
we have to fail one of them, e.g a staged session is blocking a
rollback or rollback will be causing API downgrade which will break
another staged session (b/163734200).

Bug: 163039465
Test: atest atest RollbackManagerHostTest#testRollbackFailsBlockingSessions
Test: atest StagedInstallTest
Change-Id: Ia05350024093cd537e8ced5ea02af5853620d6ef

api/current.txt

@@ -11901,8 +11901,8 @@ package android.content.pm {
     field public static final android.os.Parcelable.Creator<android.content.pm.PackageInstaller.SessionInfo> CREATOR;
     field public static final int INVALID_ID = -1; // 0xffffffff
     field public static final int STAGED_SESSION_ACTIVATION_FAILED = 2; // 0x2
+    field public static final int STAGED_SESSION_CONFLICT = 4; // 0x4
     field public static final int STAGED_SESSION_NO_ERROR = 0; // 0x0
-    field public static final int STAGED_SESSION_OTHER_ERROR = 4; // 0x4
     field public static final int STAGED_SESSION_UNKNOWN = 3; // 0x3
     field public static final int STAGED_SESSION_VERIFICATION_FAILED = 1; // 0x1
   }

core/java/android/content/pm/PackageInstaller.java

@@ -2076,7 +2076,7 @@ public class PackageInstaller {
                 STAGED_SESSION_VERIFICATION_FAILED,
                 STAGED_SESSION_ACTIVATION_FAILED,
                 STAGED_SESSION_UNKNOWN,
-                STAGED_SESSION_OTHER_ERROR})
+                STAGED_SESSION_CONFLICT})
         @Retention(RetentionPolicy.SOURCE)
         public @interface StagedSessionErrorCode{}
         /**
@@ -2103,10 +2103,10 @@ public class PackageInstaller {
         public static final int STAGED_SESSION_UNKNOWN = 3;
 
         /**
-         * Constant indicating that a known error occurred while processing this staged session, but
-         * the error could not be matched to other categories.
+         * Constant indicating that the session was in conflict with another staged session and had
+         * to be sacrificed for resolution.
          */
-        public static final int STAGED_SESSION_OTHER_ERROR = 4;
+        public static final int STAGED_SESSION_CONFLICT = 4;
 
         /** {@hide} */
         @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023)

non-updatable-api/current.txt

@@ -11901,8 +11901,8 @@ package android.content.pm {
     field public static final android.os.Parcelable.Creator<android.content.pm.PackageInstaller.SessionInfo> CREATOR;
     field public static final int INVALID_ID = -1; // 0xffffffff
     field public static final int STAGED_SESSION_ACTIVATION_FAILED = 2; // 0x2
+    field public static final int STAGED_SESSION_CONFLICT = 4; // 0x4
     field public static final int STAGED_SESSION_NO_ERROR = 0; // 0x0
-    field public static final int STAGED_SESSION_OTHER_ERROR = 4; // 0x4
     field public static final int STAGED_SESSION_UNKNOWN = 3; // 0x3
     field public static final int STAGED_SESSION_VERIFICATION_FAILED = 1; // 0x1
   }

services/core/java/com/android/server/pm/StagingManager.java

@@ -957,7 +957,7 @@ public class StagingManager {
                             // will be deleted.
                         }
                         root.setStagedSessionFailed(
-                                SessionInfo.STAGED_SESSION_OTHER_ERROR,
+                                SessionInfo.STAGED_SESSION_CONFLICT,
                                 "Session was blocking rollback session: " + session.sessionId);
                         Slog.i(TAG, "Session " + root.sessionId + " is marked failed due to "
                                 + "blocking rollback session: " + session.sessionId);