[Android] Add proxy for Java-based WebContentsObservers

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

Index: base/android/java/src/org/chromium/base/ObserverList.java
diff --git a/base/android/java/src/org/chromium/base/ObserverList.java b/base/android/java/src/org/chromium/base/ObserverList.java
index e812b0de4341e0ac21fed05c71b1a268abb18c0d..5c893217751845a4257fec795f5d50d2ad3d90b1 100644
--- a/base/android/java/src/org/chromium/base/ObserverList.java
+++ b/base/android/java/src/org/chromium/base/ObserverList.java
@@ -4,240 +4,23 @@
 
 package org.chromium.base;
 
-import java.util.ArrayList;
-import java.util.Iterator;
-import java.util.List;
-import java.util.NoSuchElementException;
-
-import javax.annotation.concurrent.NotThreadSafe;
-
 /**
- * A container for a list of observers.
- * <p/>
- * This container can be modified during iteration without invalidating the iterator.
- * So, it safely handles the case of an observer removing itself or other observers from the list
- * while observers are being notified.
- * <p/>
- * The implementation (and the interface) is heavily influenced by the C++ ObserverList.
- * Notable differences:
- *   - The iterator implements NOTIFY_EXISTING_ONLY.
- *   - The FOR_EACH_OBSERVER closure is left to the clients to implement in terms of iterator().
- * <p/>
- * This class is not threadsafe. Observers MUST be added, removed and will be notified on the same
- * thread this is created.
+ * A container for a list of observers. See BaseObserverList for details.
  *
  * @param <E> The type of observers that this list should hold.
  */
-@NotThreadSafe
-public class ObserverList<E> implements Iterable<E> {
-    /**
-     * Extended iterator interface that provides rewind functionality.
-     */
-    public interface RewindableIterator<E> extends Iterator<E> {
-        /**
-         * Rewind the iterator back to the beginning.
-         *
-         * If we need to iterate multiple times, we can avoid iterator object reallocation by using
-         * this method.
-         */
-        public void rewind();
-    }
-
-    public final List<E> mObservers = new ArrayList<E>();
-    private int mIterationDepth = 0;
-    private int mCount = 0;
+public class ObserverList<E> extends BaseObserverList<E, E> {
 
     public ObserverList() {}
 
-    /**
-     * Add an observer to the list.
-     * <p/>
-     * An observer should not be added to the same list more than once. If an iteration is already
-     * in progress, this observer will be not be visible during that iteration.
-     *
-     * @return true if the observer list changed as a result of the call.
-     */
-    public boolean addObserver(E obs) {
-        // Avoid adding null elements to the list as they may be removed on a compaction.
-        if (obs == null || mObservers.contains(obs)) {
-            return false;
-        }
-
-        // Structurally modifying the underlying list here. This means we
-        // cannot use the underlying list's iterator to iterate over the list.
-        boolean result = mObservers.add(obs);
-        assert result;
-
-        ++mCount;
-        return true;
-    }
-
-    /**
-     * Remove an observer from the list if it is in the list.
-     *
-     * @return true if an element was removed as a result of this call.
-     */
-    public boolean removeObserver(E obs) {
-        if (obs == null) {
-            return false;
-        }
-
-        int index = mObservers.indexOf(obs);
-        if (index == -1) {
-            return false;
-        }
-
-        if (mIterationDepth == 0) {
-            // No one is iterating over the list.
-            mObservers.remove(index);
-        } else {
-            mObservers.set(index, null);
-        }
-        --mCount;
-        assert mCount >= 0;
-
-        return true;
-    }
-
-    public boolean hasObserver(E obs) {
-        return mObservers.contains(obs);
-    }
-
-    public void clear() {
-        mCount = 0;
-
-        if (mIterationDepth == 0) {
-            mObservers.clear();
-            return;
-        }
-
-        int size = mObservers.size();
-        for (int i = 0; i < size; i++) {
-            mObservers.set(i, null);
-        }
-    }
-
     @Override
-    public Iterator<E> iterator() {
-        return new ObserverListIterator();
-    }
-
-    /**
-     * It's the same as {@link ObserverList#iterator()} but the return type is
-     * {@link RewindableIterator}. Use this iterator type if you need to use
-     * {@link RewindableIterator#rewind()}.
-     */
-    public RewindableIterator<E> rewindableIterator() {
-        return new ObserverListIterator();
-    }
-
-    /**
-     * Returns the number of observers currently registered in the ObserverList.
-     * This is equivalent to the number of non-empty spaces in |mObservers|.
-     */
-    public int size() {
-        return mCount;
+    final E wrap(E obs) {
+        return obs;
     }
 
-    /**
-     * Returns true if the ObserverList contains no observers.
-     */
-    public boolean isEmpty() {
-        return mCount == 0;
-    }
-
-    /**
-     * Compact the underlying list be removing null elements.
-     * <p/>
-     * Should only be called when mIterationDepth is zero.
-     */
-    private void compact() {
-        assert mIterationDepth == 0;
-        for (int i = mObservers.size() - 1; i >= 0; i--) {
-            if (mObservers.get(i) == null) {
-                mObservers.remove(i);
-            }
-        }
-    }
-
-    private void incrementIterationDepth() {
-        mIterationDepth++;
-    }
-
-    private void decrementIterationDepthAndCompactIfNeeded() {
-        mIterationDepth--;
-        assert mIterationDepth >= 0;
-        if (mIterationDepth == 0) compact();
-    }
-
-    /**
-     * Returns the size of the underlying storage of the ObserverList.
-     * It will take into account the empty spaces inside |mObservers|.
-     */
-    private int capacity() {
-        return mObservers.size();
-    }
-
-    private E getObserverAt(int index) {
-        return mObservers.get(index);
-    }
-
-    private class ObserverListIterator implements RewindableIterator<E> {
-        private int mListEndMarker;
-        private int mIndex = 0;
-        private boolean mIsExhausted = false;
-
-        private ObserverListIterator() {
-            ObserverList.this.incrementIterationDepth();
-            mListEndMarker = ObserverList.this.capacity();
-        }
-
-        @Override
-        public void rewind() {
-            compactListIfNeeded();
-            ObserverList.this.incrementIterationDepth();
-            mListEndMarker = ObserverList.this.capacity();
-            mIsExhausted = false;
-            mIndex = 0;
-        }
-
-        @Override
-        public boolean hasNext() {
-            int lookupIndex = mIndex;
-            while (lookupIndex < mListEndMarker
-                    && ObserverList.this.getObserverAt(lookupIndex) == null) {
-                lookupIndex++;
-            }
-            if (lookupIndex < mListEndMarker) return true;
-
-            // We have reached the end of the list, allow for compaction.
-            compactListIfNeeded();
-            return false;
-        }
-
-        @Override
-        public E next() {
-            // Advance if the current element is null.
-            while (mIndex < mListEndMarker && ObserverList.this.getObserverAt(mIndex) == null) {
-                mIndex++;
-            }
-            if (mIndex < mListEndMarker) return ObserverList.this.getObserverAt(mIndex++);
-
-            // We have reached the end of the list, allow for compaction.
-            compactListIfNeeded();
-            throw new NoSuchElementException();
-        }
-
-        @Override
-        public void remove() {
-            throw new UnsupportedOperationException();
-        }
-
-        private void compactListIfNeeded() {
-            if (!mIsExhausted) {
-                mIsExhausted = true;
-                ObserverList.this.decrementIterationDepthAndCompactIfNeeded();
-            }
-        }
+    @Override
+    final E unwrap(E wrapper) {
+        return wrapper;
     }
 }
+