GN(android): Add scripts & runtime logic for installing _managed apks

base/android/java/debug_src/org/chromium/base/IncrementalInstall.java

+// 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;
+
+import android.content.Context;
+
+import java.io.File;
+import java.util.List;
+
+/**
+ * Contains hooks for making Incremental Install work. Incremental Install is
+ * where native libraries and (TODO) .dex files are pushed out-of-band to
+ * external storage rather than packaged with the app.
+ */
+public final class IncrementalInstall {
+    private static final String MANAGED_DIR_PREFIX = "/data/local/tmp/incremental-app-";
+
+    public static void initialize(Context context) {
+        File incrementalAppDir = new File(MANAGED_DIR_PREFIX + context.getPackageName());
+        File incrementalLibDir = new File(incrementalAppDir, "lib");
+        injectNativeLibDir(context.getClassLoader(), incrementalLibDir);
+    }
+
+    @SuppressWarnings("unchecked")
+    private static void injectNativeLibDir(ClassLoader loader, File nativeLibDir) {
+        try {
+            Object dexPathList = Reflect.getField(loader, "pathList");
+            Object currentDirs = Reflect.getField(dexPathList, "nativeLibraryDirectories");
+            if (currentDirs instanceof List) {

[nyquist, 2015/08/26 05:23:54]

Optional nit: Care to add a comment as to when these two cases exist in the
ClassLoader? Could be helpful in the future if we want to deprecate an old
Android version.

[agrieve, 2015/08/28 14:43:29]

Going to skip on this for now just because I don't actually know when the
changeover happens, and because it's possible that we won't even need this code
once we add in .dex loading.

+                List<File> dirsAsList = (List<File>) currentDirs;
+                dirsAsList.add(nativeLibDir);
+            } else {
+                File[] dirsAsArray = (File[]) currentDirs;
+                File[] newDirs = new File[] {
+                        nativeLibDir
+                };
+                Reflect.setField(dexPathList, "nativeLibraryDirectories",
+                        Reflect.concatArrays(dirsAsArray, newDirs));
+            }
+        } catch (NoSuchFieldException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}