Changes on the ContentCaptureContext APIs.

- Replaced URI by a generic ID
  (which is a new class LocusId, and required)
- Createad a new Intent.ACTION_VIEW_LOCUS action
  (and Intent.EXTRA_LOCUS_ID extra)
- Removed ContentCaptureContext.getAction()
  (so the only "supported" action is ACTION_VIEW_LOCUS)
- Made the ContentCaptureContext getters public
  (getId(), getExtras())

Test: m update-api
Test: atest CtsContentCaptureServiceTestCases \
      CtsContentTestCases:LocusIdTest \
      FrameworksCoreTests:android.view.contentcapture.ContentCaptureEventTest

Bug: 123577059
Fixes: 124266664

Change-Id: Id4c28f056eb7a24dd083303ffdea7cf662cefac2
diff --git a/core/java/android/content/LocusId.java b/core/java/android/content/LocusId.java
new file mode 100644
index 0000000..9548f9c
--- /dev/null
+++ b/core/java/android/content/LocusId.java
@@ -0,0 +1,115 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package android.content;
+
+import android.annotation.NonNull;
+import android.net.Uri;
+import android.os.Parcel;
+import android.os.Parcelable;
+
+import com.android.internal.util.Preconditions;
+
+import java.io.PrintWriter;
+
+/**
+ * Identifier for an unique state in the application.
+ *
+ * <p>Should be stable across reboots and backup / restore.
+ *
+ * <p>For example, a chat app could use the context to resume a conversation between 2 users.
+ */
+// TODO(b/123577059): make sure this is well documented and understandable
+public final class LocusId implements Parcelable {
+
+    private final Uri mUri;
+
+    /**
+     * Default constructor.
+     */
+    public LocusId(@NonNull Uri uri) {
+        mUri = Preconditions.checkNotNull(uri);
+    }
+
+    /**
+     * Gets the {@code uri} associated with the locus.
+     */
+    @NonNull
+    public Uri getUri() {
+        return mUri;
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((mUri == null) ? 0 : mUri.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) return true;
+        if (obj == null) return false;
+        if (getClass() != obj.getClass()) return false;
+        final LocusId other = (LocusId) obj;
+        if (mUri == null) {
+            if (other.mUri != null) return false;
+        } else {
+            if (!mUri.equals(other.mUri)) return false;
+        }
+        return true;
+    }
+
+    @Override
+    public String toString() {
+        return "LocusId[uri=" + getSanitizedUri() + "]";
+    }
+
+    /** @hide */
+    public void dump(@NonNull PrintWriter pw) {
+        pw.print("uri:"); pw.println(getSanitizedUri());
+    }
+
+    private String getSanitizedUri() {
+        final int size = mUri.toString().length();
+        return size + "_chars";
+    }
+
+    @Override
+    public int describeContents() {
+        return 0;
+    }
+
+    @Override
+    public void writeToParcel(Parcel dest, int flags) {
+        dest.writeParcelable(mUri, flags);
+    }
+
+    public static final Parcelable.Creator<LocusId> CREATOR =
+            new Parcelable.Creator<LocusId>() {
+
+        @Override
+        public LocusId createFromParcel(Parcel source) {
+            final Uri uri = source.readParcelable(null);
+            return new LocusId(uri);
+        }
+
+        @Override
+        public LocusId[] newArray(int size) {
+            return new LocusId[size];
+        }
+    };
+}