Revert "Revert "Make sure that const-class linkage is preserved.""

Fix jdwp getting multiple instances of the same class.
Fix counting "zygote"/"non-zygote" classes in class table.
Fix FindClass() to EnsureResolved() classes added by
a racing thread to the class table.

Test: m test-art-host
Test: art/tools/run-jdwp-tests.sh --mode=host --variant=X64 --debug
Bug: 30627598

This reverts commit ecffc67068a28d55d131553bf915fdb9fafbbc03.

Change-Id: I15807949da4f163c2693fac2fbfc274f17685f8a
diff --git a/test/626-const-class-linking/src/RacyMisbehavingLoader.java b/test/626-const-class-linking/src/RacyMisbehavingLoader.java
new file mode 100644
index 0000000..d09888e
--- /dev/null
+++ b/test/626-const-class-linking/src/RacyMisbehavingLoader.java
@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+
+public class RacyMisbehavingLoader extends DefiningLoader {
+    static {
+        // For JVM, register as parallel capable.
+        // Android treats all class loaders as parallel capable and makes this a no-op.
+        registerAsParallelCapable();
+    }
+
+    private Object lock = new Object();
+    private int index = 0;
+    private int count;
+    private boolean throw_error;
+
+    private DefiningLoader[] defining_loaders;
+
+    public RacyMisbehavingLoader(ClassLoader parent, int count, boolean throw_error) {
+        super(parent);
+        this.count = count;
+        this.throw_error = throw_error;
+        defining_loaders = new DefiningLoader[2];
+        for (int i = 0; i != defining_loaders.length; ++i) {
+            defining_loaders[i] = new DefiningLoader(parent);
+        }
+    }
+
+    public void reportAfterLoading() {
+        synchronized (lock) {
+            ++index;
+            if (index == 2 * count) {
+                lock.notifyAll();
+            }
+        }
+    }
+
+    protected Class<?> findClass(String name) throws ClassNotFoundException
+    {
+        if (name.equals("Test")) {
+            throw new Error("Unexpected RacyLoader.findClass(\"" + name + "\")");
+        }
+        return super.findClass(name);
+    }
+
+    protected Class<?> loadClass(String name, boolean resolve)
+        throws ClassNotFoundException
+    {
+        if (name.equals("Test")) {
+            int my_index = syncWithOtherInstances(count);
+            Class<?> result;
+            if ((my_index & 1) == 0) {
+              // Do not delay loading the correct class.
+              result = defining_loaders[my_index & 1].loadClass(name, resolve);
+            } else {
+              // Delay loading the wrong class.
+              syncWithOtherInstances(2 * count);
+              if (throw_error) {
+                throw new Error("RacyMisbehavingLoader throw_error=true");
+              }
+              result = defining_loaders[my_index & 1].loadClass("Test3", resolve);
+            }
+            return result;
+        }
+        return super.loadClass(name, resolve);
+    }
+
+    private int syncWithOtherInstances(int limit) {
+        int my_index;
+        synchronized (lock) {
+            my_index = index;
+            ++index;
+            if (index != limit) {
+                try {
+                    lock.wait(2000);
+                    if (index < limit) {
+                        throw new Error("Timed out; my_index=" + my_index + ", index=" + index);
+                    }
+                } catch (InterruptedException ie) {
+                    throw new Error(ie);
+                }
+            } else {
+                lock.notifyAll();
+            }
+        }
+        return my_index;
+    }
+}