Add API for custom library loading

components/cronet/android/api/src/org/chromium/net/CronetEngine.java

Index: components/cronet/android/api/src/org/chromium/net/CronetEngine.java
diff --git a/components/cronet/android/api/src/org/chromium/net/CronetEngine.java b/components/cronet/android/api/src/org/chromium/net/CronetEngine.java
index 6336533491fe1c048429edb41211dcd51e33b7d6..e77ce4131dad545c04bceff9d25e0a8fce9da2cd 100644
--- a/components/cronet/android/api/src/org/chromium/net/CronetEngine.java
+++ b/components/cronet/android/api/src/org/chromium/net/CronetEngine.java
@@ -41,6 +41,21 @@ public abstract class CronetEngine {
      * 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.
@@ -86,6 +101,7 @@ public abstract class CronetEngine {
         private String mUserAgent;
         private String mStoragePath;
         private boolean mLegacyModeEnabled;
+        private CustomLibraryLoader mLibraryLoader;
         private String mLibraryName;
         private boolean mQuicEnabled;
         private boolean mHttp2Enabled;
@@ -187,8 +203,21 @@ public abstract class CronetEngine {
             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);
+            }
         }
 
         /**