Add API for custom library loading

components/cronet/android/test/javatests/src/org/chromium/net/CronetUrlRequestContextTest.java

Index: components/cronet/android/test/javatests/src/org/chromium/net/CronetUrlRequestContextTest.java
diff --git a/components/cronet/android/test/javatests/src/org/chromium/net/CronetUrlRequestContextTest.java b/components/cronet/android/test/javatests/src/org/chromium/net/CronetUrlRequestContextTest.java
index ce07d6bdca5eb22145ced74721f3991f8d7bd926..d533de4fe1282025fe377274729bf3dfab78dd65 100644
--- a/components/cronet/android/test/javatests/src/org/chromium/net/CronetUrlRequestContextTest.java
+++ b/components/cronet/android/test/javatests/src/org/chromium/net/CronetUrlRequestContextTest.java
@@ -960,4 +960,45 @@ public class CronetUrlRequestContextTest extends CronetTestBase {
     // Verifies that CronetEngine.Builder config from testCronetEngineBuilderConfig() is properly
     // translated to a native UrlRequestContextConfig.
     private static native void nativeVerifyUrlRequestContextConfig(long config, String storagePath);
+
+    private static class TestBadLibraryLoader extends CronetEngine.Builder.LibraryLoader {
+        public void loadLibrary(Context context, String name) {
+            // Don't do anything
+        }
+    }
+
+    @SmallTest
+    @Feature({"Cronet"})
+    public void testSkipLibraryLoading() throws Exception {
+        CronetEngine.Builder builder = new CronetEngine.Builder(getContext());
+        builder.setLibraryLoader(new TestBadLibraryLoader()).setLibraryName("cronet_tests");
+        try {
+            // ensureInitialized() calls native code to check the version right after library load
+            // and will error with the message below if library loading was skipped
+            CronetLibraryLoader.ensureInitialized(getContext(), builder);
+            fail("Native library should not be loaded");
+        } catch (UnsatisfiedLinkError e) {
+            assertTrue(e.getMessage().contains(
+                    "No implementation found for java.lang.String org.chromium.net"));
+        }
+    }
+
+    private static class TestCustomLibraryLoader extends CronetEngine.Builder.LibraryLoader {
+        public void loadLibrary(Context context, String name) {
+            // Ignore the given name, always load the test library
+            System.loadLibrary("cronet_tests");
+        }
+    }
+
+    @SmallTest
+    @Feature({"Cronet"})
+    public void testOverrideLibraryLoading() throws Exception {
+        CronetEngine.Builder builder = new CronetEngine.Builder(getContext());
+        // Don't tell the builder directly that it needs to load the test library
+        // Instead, let the custom library loader do that
+        builder.setLibraryLoader(new TestCustomLibraryLoader()).build();
+        nativeLibraryExists();

[xunjieli, 2016/01/21 19:50:53]

How does this work? The Builder.loadLibrary has not been invoked, right? How can
we call the native function?

[mgersh, 2016/01/22 17:41:16]

It gets invoked during the call to build(), through ensureInitialized(), which
is called in the CronetUrlRequestContext constructor, which is used by
reflection. Is this not expected behavior?

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

Ah, yes, you are right. There are plenty of tests where loading the native
library is a prerequisite, so I don't think we gain anything extra by having
this test. You could add a variable in TestBadLibraryLoader, set it in
loadLibrary(). And at the end of testSkipLibraryLoading(), assert it is set.
That would serve as a proof that loadLibrary is indeed called (besides the
UnsatisfiedLinkError). That one test(testSkipLibraryLoading) should be
sufficient.

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

Done.

+    }
+
+    private static native void nativeLibraryExists();
 }