fix: calc visible points on update #10467

[dangreen]

Fix #10467

[kurkle]

What breaks if it always uses <=?

My thought was to make sure the .hi is always the last (and .lo first) in case there are multiple equal values.

That said, I do not know if it would be easy to do or if it would result in slower code.

Would you be willing to ty it out?

[dangreen]

@kurkle

What breaks if it always uses <=?

Tests are failing

Details

Plugin.decimation
    lttb
      ✗ should draw all element only in range
	Error: Expected 3 to be 2.
	    at <Jasmine>
	    at UserContext.<anonymous> (test/specs/plugin.decimation.tests.js:176:48)
	    at <Jasmine>

	Error: Expected 4 to be 3.
	    at <Jasmine>
	    at UserContext.<anonymous> (test/specs/plugin.decimation.tests.js:177:48)
	    at <Jasmine>

	Error: Expected 5 to be 4.
	    at <Jasmine>
	    at UserContext.<anonymous> (test/specs/plugin.decimation.tests.js:178:48)
	    at <Jasmine>

	Error: Expected 6 to be 5.
	    at <Jasmine>
	    at UserContext.<anonymous> (test/specs/plugin.decimation.tests.js:179:48)
	    at <Jasmine>

	Error: Expected 7 to be 6.
	    at <Jasmine>
	    at UserContext.<anonymous> (test/specs/plugin.decimation.tests.js:180:48)
	    at <Jasmine>