Apple 15 inch MacBook Pros from mid 2010 were manufactured with some hardware defects causing it to intermittently freeze or stop displaying video on the built-in or external display. Apple has been replacing affected machines' motherboards, but the problem seems to persist even afterwards, but less frequently.
Any program that makes the system switch graphics processor can trigger the defect. Typically, for example, the system starts up using the Intel integrated graphics, then you open Chrome, which kicks it over to the Nvidia discrete graphics. Later, you quit Chrome and when it switches back to the Intel integrated graphics, the screen may now flicker and then go black.
Strangely enough, a workaround exists. Sleep the computer at least once after starting up. Once it's gone to sleep at least once, the defeat seems to no longer be triggered upon graphics switching.