Reland: Add basic support for Ctrl-Z to editable TextViews

Reland 9201e797833f35b9afb219f88c10d3b6fda02a4e which was reverted in
c8f08e07a47cc259a25caed3f731ee7044328635.

Original description:
* Add an UndoManager to the Editor for each editable TextView
* Record operations as being owned by that Editor
* Parcel the undo state
* Wire hardware keyboard shortcuts Ctrl-Z for undo and Ctrl-Shift-Z
  for redo into TextView shortcut handling.
* Expose IDs for "undo" and "redo" for symmetry with cut/copy/paste.

Additional fix:
* Ensure each UndoOwner always has a valid mManager, even after the
  UndoManager is parceled and restored.

Bug: 19332904
Bug: 19505388
Change-Id: Iad4476e6e9ca952281e69bf22c07cca915dfa7bd

2 files changed, 11 insertions, 6 deletions

diff --git a/core/java/android/content/UndoManager.java b/core/java/android/content/UndoManager.java
index e3bc238..559b01c 100644
--- a/core/java/android/content/UndoManager.java
+++ b/core/java/android/content/UndoManager.java
@@ -105,8 +105,7 @@ public class UndoManager {
             return owner;
         }
 
-        owner = new UndoOwner(tag);
-        owner.mManager = this;
+        owner = new UndoOwner(tag, this);
         owner.mData = data;
         mOwners.put(tag, owner);
         return owner;
@@ -116,7 +115,6 @@ public class UndoManager {
         // XXX need to figure out how to prune.
         if (false) {
             mOwners.remove(owner.mTag);
-            owner.mManager = null;
         }
     }
 
@@ -202,7 +200,7 @@ public class UndoManager {
         UndoOwner owner = mStateOwners[idx];
         if (owner == null) {
             String tag = in.readString();
-            owner = new UndoOwner(tag);
+            owner = new UndoOwner(tag, this);
             mStateOwners[idx] = owner;
             mOwners.put(tag, owner);
         }
diff --git a/core/java/android/content/UndoOwner.java b/core/java/android/content/UndoOwner.java
index d0cdc95..9106588 100644
--- a/core/java/android/content/UndoOwner.java
+++ b/core/java/android/content/UndoOwner.java
@@ -23,8 +23,8 @@ package android.content;
  */
 public class UndoOwner {
     final String mTag;
+    final UndoManager mManager;
 
-    UndoManager mManager;
     Object mData;
     int mOpCount;
 
@@ -32,8 +32,15 @@ public class UndoOwner {
     int mStateSeq;
     int mSavedIdx;
 
-    UndoOwner(String tag) {
+    UndoOwner(String tag, UndoManager manager) {
+        if (tag == null) {
+            throw new NullPointerException("tag can't be null");
+        }
+        if (manager == null) {
+            throw new NullPointerException("manager can't be null");
+        }
         mTag = tag;
+        mManager = manager;
     }
 
     /**