[Android] Rework multidex and enable multidex for unit_tests_apk.

base/android/java/templates/ChromiumMultiDex.template

 // Copyright 2015 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.multidex;
 
-import android.app.ActivityManager;
-import android.app.ActivityManager.RunningAppProcessInfo;
-import android.content.Context;
-import android.content.pm.ApplicationInfo;
-import android.content.pm.PackageManager;
-import android.os.Build;
-import android.os.Process;
-import android.support.multidex.MultiDex;
+/**
+ *  Multidex configuration. Generated on a per-target basis.
+ */
+class ChromiumMultiDex {
 
-import org.chromium.base.Log;
-import org.chromium.base.VisibleForTesting;
-
-import java.lang.reflect.InvocationTargetException;
-import java.lang.reflect.Method;
-
-/**
- *  Performs multidex installation for non-isolated processes.
- */
-public class ChromiumMultiDex {
-
-    private static final String TAG = "base_multidex";
-
-    /**
-     * Suffix for the meta-data tag in the AndroidManifext.xml that determines whether loading
-     * secondary dexes should be skipped for a given process name.
+    /** Whether multidex is enabled for this target.
+     *
+     *  This has to be a function instead of a static final boolean s.t. the initial false value
+     *  doesn't get optimized into {@link ChromiumMultiDexInstaller} at base_java compile time.
      */
-    private static final String IGNORE_MULTIDEX_KEY = ".ignore_multidex";
-
-    /**
-     *  Installs secondary dexes if possible/necessary.
-     *
-     *  Isolated processes (e.g. renderer processes) can't load secondary dex files on
-     *  K and below, so we don't even try in that case.
-     *
-     *  In release builds, this is a no-op because:
-     *    - multidex isn't necessary in release builds because we run proguard there and
-     *      thus aren't threatening to hit the dex limit; and
-     *    - calling MultiDex.install, even in the absence of secondary dexes, causes a
-     *      significant regression in start-up time (crbug.com/525695).
-     *
-     *  @param context The application context.
-     */
-    @VisibleForTesting
-#if defined(MULTIDEX_CONFIGURATION_Debug)
-    public static void install(Context context) {
-        // TODO(jbudorick): Back out this version check once support for K & below works.
-        // http://crbug.com/512357
-        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP
-                && !shouldInstallMultiDex(context)) {
-            Log.i(TAG, "Skipping multidex installation: not needed for process.");
-        } else {
-            MultiDex.install(context);
-            Log.i(TAG, "Completed multidex installation.");
-        }
+    static boolean isMultidexEnabled() {
+#if defined(ENABLE_MULTIDEX)
+        return true;
+#else
+        return false;
+#endif
     }
 
-    private static String getProcessName(Context context) {
-        try {
-            String currentProcessName = null;
-            int pid = android.os.Process.myPid();
-
-            ActivityManager manager =
-                    (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
-            for (RunningAppProcessInfo processInfo : manager.getRunningAppProcesses()) {
-                if (processInfo.pid == pid) {
-                    currentProcessName = processInfo.processName;
-                    break;
-                }
-            }
-
-            return currentProcessName;
-        } catch (SecurityException ex) {
-            return null;
-        }
-    }
-
-    // Determines whether MultiDex should be installed for the current process.  Isolated
-    // Processes should skip MultiDex as they can not actually access the files on disk.
-    // Privileged processes need ot have all of their dependencies in the MainDex for
-    // performance reasons. 
-    private static boolean shouldInstallMultiDex(Context context) {
-        try {
-            Method isIsolatedMethod =
-                    android.os.Process.class.getMethod("isIsolated");
-            Object retVal = isIsolatedMethod.invoke(null);
-            if (retVal != null && retVal instanceof Boolean && ((Boolean) retVal)) {
-                return false;
-            }
-        } catch (IllegalAccessException | IllegalArgumentException
-                | InvocationTargetException | NoSuchMethodException e) {
-            // Ignore and fall back to checking the app processes.
-        }
-
-        String currentProcessName = getProcessName(context);
-        if (currentProcessName == null) return true;
-        
-        PackageManager packageManager = context.getPackageManager();
-        try {
-            ApplicationInfo appInfo = packageManager.getApplicationInfo(context.getPackageName(),
-                    PackageManager.GET_META_DATA);
-            if (appInfo == null || appInfo.metaData == null) return true;
-            return !appInfo.metaData.getBoolean(currentProcessName + IGNORE_MULTIDEX_KEY, false);
-        } catch (PackageManager.NameNotFoundException e) {
-            return true;
-        }
-    }
-#else
-    public static void install(Context context) {
-    }
-#endif
-
 }