cronet: Do not hide symbols on Android shared build

The default compiler config hides all but JNI symbols, but here
it is building the shared library of Cronet C API.

src/components/cronet/BUILD.gn

@@ -137,6 +137,10 @@ if (is_android) {
       ]
       public_configs = [ ":shared_library_public_config" ]
     }
+
+    if (is_android) {
+      configs -= [ "//build/config/android:hide_all_but_jni_onload" ]
+    }
   }
 
   test("cronet_tests") {