simpleperf: improve report html interface.

1. Store record data in a json script element.
2. Simplify the title of SampleTableTab.
3. Split the logic selecting how to show sample weight
   in a separate class FunctionSampleWeightSelectorView.
   And provide a sampleWeightFunction instead of totalEventCount,
   which is more flexible.
4. Adjust the way to implement IIFE.

Bug: http://b/66914187
Test: run report_html.py manually.
Test: run test.py.

Change-Id: Ibfe221c74f15a554ad4f7be49801de7e5af95a86
2 files changed