[Cronet] Add proguard files for different Cronet packaging

components/cronet/android/cronet_impl_native_proguard.cfg

+# Proguard config for apps that depend on cronet_impl_native_java.jar.
+
 -keep class org.chromium.net.impl.CronetUrlRequest$HeadersList
 -keep class org.chromium.net.impl.ChromiumUrlRequest$ResponseHeadersMap
 
-# This constructor is called by the reflection from Cronet API. It cannot be
-# annotated with @org.chromium.base.annotations.AccessedByNative in order to
-# avoid the dependency on Chromium-Base Java classes.
--keep class org.chromium.net.impl.CronetEngineBuilderImpl {
-    public <init>(android.content.Context);
-}
-
 # Suppress unnecessary warnings.
 -dontnote org.chromium.net.ProxyChangeListener$ProxyReceiver
 -dontnote org.chromium.net.AndroidKeyStore
 # Needs 'void setTextAppearance(int)' (API level 23).
 -dontwarn org.chromium.base.ApiCompatibilityUtils
 # Needs 'boolean onSearchRequested(android.view.SearchEvent)' (API level 23).
 -dontwarn org.chromium.base.WindowCallbackWrapper
 
 # Generated for chrome apk and not included into cronet.
 -dontwarn org.chromium.base.BuildConfig
 -dontwarn org.chromium.base.library_loader.NativeLibraries
 -dontwarn org.chromium.base.multidex.ChromiumMultiDexInstaller
 
 # Objects of this type are passed around by native code, but the class
 # is never used directly by native code. Since the class is not loaded, it does
 # not need to be preserved as an entry point.
 -dontnote org.chromium.net.UrlRequest$ResponseHeadersMap
 # https://android.googlesource.com/platform/sdk/+/marshmallow-mr1-release/files/proguard-android.txt#54
 -dontwarn android.support.**