Cherry-pick "Don't register JNI methods for the android_webview."

> Rather than registering all jni bindings at startup, only get references
> to the class object for those files which require bindings. All others
> are satisfied by exporting symbols which can be found automatically by
> the VM.
>
> BUG=402003
>
> Review URL: https://codereview.chromium.org/454923002

BUG: 16870075
Change-Id: I8d7617c87ac10cb9833cdb370bc6718bd58fd587
8 files changed