[Android] Enable multidex for release builds of chrome_public_test_apk.

base/test/android/javatests/src/org/chromium/base/test/BaseChromiumRunnerCommon.java

Index: base/test/android/javatests/src/org/chromium/base/test/BaseChromiumRunnerCommon.java
diff --git a/base/test/android/javatests/src/org/chromium/base/test/BaseChromiumRunnerCommon.java b/base/test/android/javatests/src/org/chromium/base/test/BaseChromiumRunnerCommon.java
new file mode 100644
index 0000000000000000000000000000000000000000..d5a919bc64954c919f26e732ff96a15f19eb3580
--- /dev/null
+++ b/base/test/android/javatests/src/org/chromium/base/test/BaseChromiumRunnerCommon.java
@@ -0,0 +1,161 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.base.test;
+
+import android.content.Context;
+import android.content.ContextWrapper;
+import android.content.SharedPreferences;
+import android.content.pm.ApplicationInfo;
+import android.content.pm.PackageManager;
+
+import org.chromium.base.Log;
+import org.chromium.base.annotations.MainDex;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.Serializable;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.Comparator;
+
+/**
+ *  Functionality common to the JUnit3 and JUnit4 runners.
+ */
+@MainDex
+class BaseChromiumRunnerCommon {
+    private static final String TAG = "base_test";
+
+    /**
+     *  A ContextWrapper that allows multidex test APKs to extract secondary dexes into
+     *  the APK under test's data directory.
+     */
+    @MainDex
+    static class MultiDexContextWrapper extends ContextWrapper {
+        private Context mAppContext;
+
+        MultiDexContextWrapper(Context instrContext, Context appContext) {
+            super(instrContext);
+            mAppContext = appContext;
+        }
+
+        @Override
+        public File getFilesDir() {
+            return mAppContext.getFilesDir();
+        }
+
+        @Override
+        public SharedPreferences getSharedPreferences(String name, int mode) {
+            return mAppContext.getSharedPreferences(name, mode);
+        }
+
+        @Override
+        public PackageManager getPackageManager() {
+            return new PackageManagerWrapper(super.getPackageManager()) {
+                @Override
+                public ApplicationInfo getApplicationInfo(String packageName, int flags) {
+                    try {
+                        ApplicationInfo ai = super.getApplicationInfo(packageName, flags);
+                        if (packageName.equals(getPackageName())) {
+                            ApplicationInfo appAi =
+                                    super.getApplicationInfo(mAppContext.getPackageName(), flags);
+                            File dataDir = new File(appAi.dataDir, "test-multidex");
+                            if (!dataDir.exists() && !dataDir.mkdirs()) {
+                                throw new IOException(String.format(
+                                        "Unable to create test multidex directory \"%s\"",
+                                        dataDir.getPath()));
+                            }
+                            ai.dataDir = dataDir.getPath();
+                        }
+                        return ai;
+                    } catch (Exception e) {
+                        Log.e(TAG, "Failed to get application info for %s", packageName, e);
+                    }
+                    return null;
+                }
+            };
+        }
+    }
+
+    /**
+     * Ensure all test dex entries precede app dex entries.
+     *
+     * @param cl ClassLoader to modify. Assumed to be a derivative of
+     *        {@link dalvik.system.BaseDexClassLoader}. If this isn't
+     *        the case, reordering will fail.
+     */
+    static void reorderDexPathElements(ClassLoader cl, Context context, Context targetContext) {
+        try {
+            Log.i(TAG,
+                    "Reordering dex files. If you're building a multidex test APK and see a "
+                            + "class resolving to an unexpected implementation, this may be why.");
+            Field pathListField = findField(cl, "pathList");
+            Object dexPathList = pathListField.get(cl);
+            Field dexElementsField = findField(dexPathList, "dexElements");
+            Object[] dexElementsList = (Object[]) dexElementsField.get(dexPathList);
+            Arrays.sort(dexElementsList,
+                    new DexListReorderingComparator(
+                            context.getPackageName(), targetContext.getPackageName()));
+            dexElementsField.set(dexPathList, dexElementsList);
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to reorder dex elements for testing.", e);
+        }
+    }
+
+    /**
+     *  Comparator for sorting dex list entries.
+     *
+     *  Using this to sort a list of dex list entries will result in the following order:
+     *   - Strings that contain neither the test package nor the app package in lexicographical
+     *     order.
+     *   - Strings that contain the test package in lexicographical order.
+     *   - Strings that contain the app package but not the test package in lexicographical order.
+     */
+    private static class DexListReorderingComparator implements Comparator<Object>, Serializable {
+        private String mTestPackage;
+        private String mAppPackage;
+
+        public DexListReorderingComparator(String testPackage, String appPackage) {
+            mTestPackage = testPackage;
+            mAppPackage = appPackage;
+        }
+
+        @Override
+        public int compare(Object o1, Object o2) {
+            String s1 = o1.toString();
+            String s2 = o2.toString();
+            if (s1.contains(mTestPackage)) {
+                if (!s2.contains(mTestPackage)) {
+                    if (s2.contains(mAppPackage)) {
+                        return -1;
+                    } else {
+                        return 1;
+                    }
+                }
+            } else if (s1.contains(mAppPackage)) {
+                if (s2.contains(mTestPackage)) {
+                    return 1;
+                } else if (!s2.contains(mAppPackage)) {
+                    return 1;
+                }
+            } else if (s2.contains(mTestPackage) || s2.contains(mAppPackage)) {
+                return -1;
+            }
+            return s1.compareTo(s2);
+        }
+    }
+
+    private static Field findField(Object instance, String name) throws NoSuchFieldException {
+        for (Class<?> clazz = instance.getClass(); clazz != null; clazz = clazz.getSuperclass()) {
+            try {
+                Field f = clazz.getDeclaredField(name);
+                f.setAccessible(true);
+                return f;
+            } catch (NoSuchFieldException e) {
+            }
+        }
+        throw new NoSuchFieldException(
+                "Unable to find field " + name + " in " + instance.getClass());
+    }
+}