There are bill signings, and there are bill signings. The one for House Bill 1472 was one of the grander affairs of its kind, held “off campus” at Rainier Beach High School in Seattle and bringing together teachers, students and high-tech execs (and Gov. Inslee, of course: he brought the pen).
All those folks wanted to demonstrate their support for the bill, sponsored by Rep. Drew Hansen, which calls for school boards to approve an Advanced Placement computer-science course as equivalent to a math or science course, including for purposes of meeting math or science graduation requirements for high school. States that have treated AP computer science as a math or science course rather than an elective have seen more students enroll in AP computer science.
Gov. Inslee vigorously supports preparing students for good 21st-century jobs and generally gearing the state up for competition in the global economy. Microsoft, represented at the signing by exec VP and general counsel Brad Smith, wants a healthy in-state pool of well-trained computer programmers it can hire.
You can read more about it here.