Optional call stack depth parameter

The logging interface looks like following:

```
log(int priority, String tag, String message, Throwable t)
```

Why not add an additional call stack adjustment value?

**Use cases**

Maybe someone wants to write reuseable logging functions, that should log their calling functions parameters. Seems like a common use case for me.

**Example - simple transformer for logging observables execution time**

```
public static Observable.Transformer applyMeasurement(Class clazz, String tag, boolean enabled)
{
return observable -> measure(observable, clazz, tag, enabled);
}

private static Observable measure(Observable observable, Class clazz, String tag, boolean enabled)
{
if (!mEnabled || !enabled)
return observable;

LongHolder start = new LongHolder(0);
return observable
.doOnSubscribe(() -> start.set(System.currentTimeMillis()))
.doOnTerminate(() -> Timber.d("[%s | %s] Duration: %dms", clazz, tag, System.currentTimeMillis() - start.get()));
}
```

Here the log would print the line and class of my logger utility class, which is not perfect...

Wouldn't it make sense to extend the log interface for such use cases?

No file or test is named. Start by locating the logging interface and its delegation to Android's Log, then review the existing discussion before proposing the API shape. Done would require an agreed call-stack adjustment design and corresponding behavior coverage.

Written by the indexing model from the issue text.