Change contentEquals implementation to operate in O(n) time.

Calling other.get(key) does binary search in the "other" instance to look up the key, but this is not necessary, since if the two instances are equal, they will contain same keys with same values in exact same order.

The cl also does some other minor changes:
* avoid unnecessary method calls / bounds check in contentEquals.
* avoid unnecessary method calls / bounds check / autoboxing in
  contentHashCode.
It's possible that some of these would be done by AOT / JIT optimizations, but they generally tend to have some cost in Java.

Test: atest SparseArrayTest
Bug: 260964842

Change-Id: I060ea39e85056a86e986a0fe61d153c18c234f4b

core/java/android/util/SparseArray.java

@@ -525,9 +525,10 @@ public class SparseArray<E> implements Cloneable {
             return false;
         }
 
+        // size() calls above took care about gc() compaction.
         for (int index = 0; index < size; index++) {
-            int key = keyAt(index);
-            if (!Objects.equals(valueAt(index), other.get(key))) {
+            if (mKeys[index] != other.mKeys[index]
+                    || !Objects.equals(mValues[index], other.mValues[index])) {
                 return false;
             }
         }
@@ -545,10 +546,11 @@ public class SparseArray<E> implements Cloneable {
     public int contentHashCode() {
         int hash = 0;
         int size = size();
+        // size() call above took care about gc() compaction.
         for (int index = 0; index < size; index++) {
-            int key = keyAt(index);
-            E value = valueAt(index);
-            hash = 31 * hash + Objects.hashCode(key);
+            int key = mKeys[index];
+            E value = (E) mValues[index];
+            hash = 31 * hash + key;
             hash = 31 * hash + Objects.hashCode(value);
         }
         return hash;