Add API for custom library loading

components/cronet/android/api/src/org/chromium/net/CronetEngine.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.net;
 
 import android.content.Context;
 import android.support.annotation.IntDef;
 import android.support.annotation.Nullable;
 import android.util.Log;
@@ skipping 23 matching lines @@
  * An engine to process {@link UrlRequest}s, which uses the best HTTP stack
  * available on the current platform.
  */
 public abstract class CronetEngine {
     /**
      * A builder for {@link CronetEngine}s, which allows runtime configuration of
      * {@code CronetEngine}. Configuration options are set on the builder and
      * then {@link #build} is called to create the {@code CronetEngine}.
      */
     public static class Builder {
+        /**
+         * A callback for loading the cronet native library. Apps needing to implement custom

[xunjieli, 2016/01/22 22:53:15]

nit: s/A callback/An interface.

According to go/android-api-guidelines, we should only use interface if we are
certain that this will only contain one method. That was why I suggested
abstract class initially. But i think it is as good as of now.

[mgersh, 2016/01/25 17:31:11]

Thanks, that's a useful link. It convinced me to change it back to an abstract
class, actually--it might be technically okay to use an interface here but I
wasn't thinking of the potential downsides.

+         * library loading logic can implement this interface and pass an instance to
+         * {@link CronetEngine.Builder.setLibraryLoader()}. For example, this might be required
+         * to work around {@code UnsatisfiedLinkError}s caused by flaky installation on certain
+         * older devices.
+         */
+        public static interface CustomLibraryLoader {

[xunjieli, 2016/01/22 22:53:15]

Gonna retract my earlier comment. I think LibraryLoader is a cleaner naming.
Would you mind changing it back? :)

[mgersh, 2016/01/25 17:31:11]

Done.

+            /**
+             * Load the native library.

[xunjieli, 2016/01/22 22:53:15]

nit: s/Load/Loads

[mgersh, 2016/01/25 17:31:11]

Done.

+             * @param libName name of the library to load
+             */
+            public void loadLibrary(String libName);
+        }
+
         // A hint that a host supports QUIC.
         static class QuicHint {
             // The host.
             final String mHost;
             // Port of the server that supports QUIC.
             final int mPort;
             // Alternate protocol port.
             final int mAlternatePort;
 
             QuicHint(String host, int port, int alternatePort) {
@@ skipping 25 matching lines @@
         private static final Pattern INVALID_PKP_HOST_NAME = Pattern.compile("^[0-9\\.]*$");
 
         // Private fields are simply storage of configuration for the resulting CronetEngine.
         // See setters below for verbose descriptions.
         private final Context mContext;
         private final List<QuicHint> mQuicHints = new LinkedList<QuicHint>();
         private final List<Pkp> mPkps = new LinkedList<Pkp>();
         private String mUserAgent;
         private String mStoragePath;
         private boolean mLegacyModeEnabled;
+        private CustomLibraryLoader mLibraryLoader;
         private String mLibraryName;
         private boolean mQuicEnabled;
         private boolean mHttp2Enabled;
         private boolean mSdchEnabled;
         private String mDataReductionProxyKey;
         private String mDataReductionProxyPrimaryProxy;
         private String mDataReductionProxyFallbackProxy;
         private String mDataReductionProxySecureProxyCheckUrl;
         private boolean mDisableCache;
         private int mHttpCacheMode;
@@ skipping 81 matching lines @@
 
         /**
          * Overrides the name of the native library backing Cronet.
          * @return the builder to facilitate chaining.
          */
         Builder setLibraryName(String libName) {
             mLibraryName = libName;
             return this;
         }
 
-        String libraryName() {
-            return mLibraryName;
+        /**
+         * Overrides the callback to load the native library.

[xunjieli, 2016/01/22 22:53:15]

Maybe update the comment? something like: Sets a library loader to be used for
loading the native library. If it is not set, the library will be load using
{@link System.load()}. See {@link LibraryLoader} for more information.

[mgersh, 2016/01/25 17:31:11]

Done.

+         * @return the builder to facilitate chaining.
+         */
+        public Builder setLibraryLoader(CustomLibraryLoader loader) {
+            mLibraryLoader = loader;
+            return this;
+        }
+
+        void loadLibrary() {
+            if (mLibraryLoader == null) {
+                System.loadLibrary(mLibraryName);
+            } else {
+                mLibraryLoader.loadLibrary(mLibraryName);
+            }
         }
 
         /**
          * Sets whether <a href="https://www.chromium.org/quic">QUIC</a> protocol
          * is enabled. Defaults to disabled.
          * @return the builder to facilitate chaining.
          */
         public Builder enableQUIC(boolean value) {
             mQuicEnabled = value;
             return this;
@@ skipping 824 matching lines @@
      * Interface to listen for finished requests that were created via this CronetEngine instance.
      *
      * @deprecated not really deprecated but hidden for now as it's a prototype.
      */
     @Deprecated
     public interface RequestFinishedListener { // TODO(klm): Add a convenience abstract class.
         /** Invoked with request info. */
         void onRequestFinished(UrlRequestInfo requestInfo);
     }
 }