[SPARK-4674] Refactor getCallSite

[viirya]

The current version of getCallSite visits the collection of StackTraceElement twice. However, it is unnecessary since we can perform our work with a single visit. We also do not need to keep filtered StackTraceElement.

[JoshRosen]

Jenkins, this is ok to test.

[SparkQA]

Test build #23994 has finished for PR 3532 at commit e741017.

• This patch fails Scala style tests.
• This patch merges cleanly.
• This patch adds no public classes.

[viirya]

Style is fixed. Please test again.

[SparkQA]

Test build #23996 has finished for PR 3532 at commit 62aa124.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[JoshRosen]

This looks good to me (most of the diff is just an indentation change), so I'm going to merge this to master (1.3.0). Thanks!

Just out of curiosity, what motivated this change? Did you notice a performance issue here?

[viirya]

Thanks. I found that getCallSite is called in many places. So I am curious about its implementation details. Then I thought it can be more efficient. I have not really tested its performance but as we can reduce the number of times of visiting the collection of StackTraceElement. It should be faster slightly.