[2/2] spark git commit: [SPARK-20657][CORE] Speed up rendering of the stages page.

[SPARK-20657][CORE] Speed up rendering of the stages page. There are two main changes to speed up rendering of the tasks list when rendering the stage page. The first one makes the code only load the tasks being shown in the current page of the tasks table, and information related to only those

[2/2] spark git commit: [SPARK-20657][CORE] Speed up rendering of the stages page.

[SPARK-20657][CORE] Speed up rendering of the stages page. There are two main changes to speed up rendering of the tasks list when rendering the stage page. The first one makes the code only load the tasks being shown in the current page of the tasks table, and information related to only those