[SPARK-21590][SS]Window start time should support negative values

[KevinZwx]

What changes were proposed in this pull request?

Remove the non-negative checks of window start time to make window support negative start time, and add a check to guarantee the absolute value of start time is less than slide duration.

How was this patch tested?

New unit tests.

[KevinZwx]

@zsxwing@brkyvz Can you review this patch?

[brkyvz]

ok to test

[brkyvz]

could you also add a DataFrame test for this with a negative value? then I'll feel a lot more comfortable that we don't have to have the start offset as a positive number in the window calculation.
Look for DataFrameTimeWindowingSuite.scala

[KevinZwx]

Yeah thanks, I added some tests in DataFrameTimeWindowingSuite

[brkyvz]

test this please

[KevinZwx]

test this please

[SparkQA]

Test build #4154 has finished for PR 18903 at commit 07e98e7.

• This patch fails PySpark unit tests.
• This patch does not merge cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #4175 has finished for PR 18903 at commit 07e98e7.

• This patch fails PySpark unit tests.
• This patch does not merge cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #4178 has finished for PR 18903 at commit 07e98e7.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[kiszk]

retest this please

[HyukjinKwon]

ok to test

[SparkQA]

Test build #93048 has finished for PR 18903 at commit 07e98e7.

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

[srowen]

Merged to master