Try to mitigate issue #31016187: system_server crash in ArraySet.

Instead of crashing, log a wtf and recover.  This is not a problem
in ArraySet, but caused by someone else using an ArraySet without
protecting access to it.  So whoever is calling at this point is
not the cause, and it isn't worthwhile to let them crash.

Change-Id: Iaefa4315b620c9fe24b31507e4aa47a8525c8540
(cherry picked from commit 92aa4b2ba3c93cc344c885b50b75726599e6065d)
(cherry picked from commit dd28b7b5f33810666919e2f9fc8deb27b7b9c169)
diff --git a/core/java/android/util/ArraySet.java b/core/java/android/util/ArraySet.java
index 1e765b6..a02c070 100644
--- a/core/java/android/util/ArraySet.java
+++ b/core/java/android/util/ArraySet.java
@@ -156,28 +156,46 @@
             synchronized (ArraySet.class) {
                 if (mTwiceBaseCache != null) {
                     final Object[] array = mTwiceBaseCache;
-                    mArray = array;
-                    mTwiceBaseCache = (Object[])array[0];
-                    mHashes = (int[])array[1];
-                    array[0] = array[1] = null;
-                    mTwiceBaseCacheSize--;
-                    if (DEBUG) Log.d(TAG, "Retrieving 2x cache " + mHashes
-                            + " now have " + mTwiceBaseCacheSize + " entries");
-                    return;
+                    try {
+                        mArray = array;
+                        mTwiceBaseCache = (Object[]) array[0];
+                        mHashes = (int[]) array[1];
+                        array[0] = array[1] = null;
+                        mTwiceBaseCacheSize--;
+                        if (DEBUG) Log.d(TAG, "Retrieving 2x cache " + mHashes
+                                + " now have " + mTwiceBaseCacheSize + " entries");
+                        return;
+                    } catch (ClassCastException e) {
+                    }
+                    // Whoops!  Someone trampled the array (probably due to not protecting
+                    // their access with a lock).  Our cache is corrupt; report and give up.
+                    Slog.wtf(TAG, "Found corrupt ArraySet cache: [0]=" + array[0]
+                            + " [1]=" + array[1]);
+                    mTwiceBaseCache = null;
+                    mTwiceBaseCacheSize = 0;
                 }
             }
         } else if (size == BASE_SIZE) {
             synchronized (ArraySet.class) {
                 if (mBaseCache != null) {
                     final Object[] array = mBaseCache;
-                    mArray = array;
-                    mBaseCache = (Object[])array[0];
-                    mHashes = (int[])array[1];
-                    array[0] = array[1] = null;
-                    mBaseCacheSize--;
-                    if (DEBUG) Log.d(TAG, "Retrieving 1x cache " + mHashes
-                            + " now have " + mBaseCacheSize + " entries");
-                    return;
+                    try {
+                        mArray = array;
+                        mBaseCache = (Object[]) array[0];
+                        mHashes = (int[]) array[1];
+                        array[0] = array[1] = null;
+                        mBaseCacheSize--;
+                        if (DEBUG) Log.d(TAG, "Retrieving 1x cache " + mHashes
+                                + " now have " + mBaseCacheSize + " entries");
+                        return;
+                    } catch (ClassCastException e) {
+                    }
+                    // Whoops!  Someone trampled the array (probably due to not protecting
+                    // their access with a lock).  Our cache is corrupt; report and give up.
+                    Slog.wtf(TAG, "Found corrupt ArraySet cache: [0]=" + array[0]
+                            + " [1]=" + array[1]);
+                    mBaseCache = null;
+                    mBaseCacheSize = 0;
                 }
             }
         }