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..0ede759184fa5decfd91dce0ff15a1dd508523fe 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 class which provides a method for loading the cronet native library. Apps needing to
+         * implement custom library loading logic can inherit from this class 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 abstract static class LibraryLoader {
+            /**
+             * Loads the native library.
+             * @param libName name of the library to load
+             */
+            public abstract 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 LibraryLoader mLibraryLoader;
         private String mLibraryName;
         private boolean mQuicEnabled;
         private boolean mHttp2Enabled;
@@ -187,8 +203,22 @@ public abstract class CronetEngine {
             return this;
         }
 
-        String libraryName() {
-            return mLibraryName;
+        /**
+         * Sets a {@link LibraryLoader} to be used to load the native library.
+         * If not set, the library will be loaded using {@link System#loadLibrary}.
+         * @return the builder to facilitate chaining.
+         */
+        public Builder setLibraryLoader(LibraryLoader loader) {
+            mLibraryLoader = loader;
+            return this;
+        }
+
+        void loadLibrary() {
+            if (mLibraryLoader == null) {
+                System.loadLibrary(mLibraryName);
+            } else {
+                mLibraryLoader.loadLibrary(mLibraryName);
+            }
         }
 
         /**