Use proguard.cfg in cronet sample apk.

components/cronet/android/sample/javatests/proguard.cfg

+# Proguard settings for CronetSampleTestApk.
+
+# Keep classes directly accessed from test apk
+-keep class org.chromium.base.library_loader.LibraryLoaderHelper {

[xunjieli, 2014/09/02 16:53:16]

It looks like the sample is only using
https://code.google.com/p/chromium/codesearch#chromium/src/components/cronet/...
, and not the LibraryLoader from base. 

Why do we need to keep this class?

[mef, 2014/09/12 20:49:24]

base_javatests include org.chromium.base.LibraryLoaderHelperTest, which uses
this class. We do need to clean that at some point.

+    void deleteWorkaroundLibrariesSynchronously(...);
+    java.io.File getWorkaroundLibDir(...);
+    boolean loadNativeLibrariesUsingWorkaroundForTesting(...);
+}
+-keep class org.chromium.base.CommandLine {

[Charles, 2014/09/02 16:52:19]

If you're keeping all these classes here, adding proguard to your tests is
unlikely to actually test anything.

[mef, 2014/09/12 20:49:24]

Good point. I think it makes sense to build CronetSample.apk with cronet
proguard.txt only to find proguard issues. We will move tests to CronetTest.apk
and that will not use proguard. 

+    *;
+}
+-keep class org.chromium.base.ObserverList* {
+    *;
+}
+-keep class org.chromium.cronet_sample_apk.CronetSampleActivity {
+    *;
+}
+-keep class org.chromium.net.ChromiumUrlRequestContext {
+    void startNetLogToFile(...);
+    void stopNetLog();
+}
+-keep class org.chromium.net.ChromiumUrlRequestFactory {
+    org.chromium.net.ChromiumUrlRequest createRequest(...);
+    org.chromium.net.ChromiumUrlRequestContext getRequestContext();
+}
+-keep class org.chromium.net.HttpUrlRequest {
+    *;
+}
+-keep class org.chromium.net.HttpUrlRequestFactory {
+    org.chromium.net.HttpUrlRequestFactory createFactory(...);
+    java.lang.String getName();
+}
+-keep class org.chromium.net.HttpUrlRequestFactoryConfig {
+    org.chromium.net.HttpUrlRequestFactoryConfig enableLegacyMode(...);
+}
+-keep class org.chromium.net.HttpUrlRequestListener {
+    *;
+}
+-keep class org.chromium.net.ChunkedWritableByteChannel {
+    *;
+}
+
+# Keep Test classes
+-keep class * extends junit.framework.TestCase {
+    *;
+}