The vast majority of HDMI ports provide the amount of power required by the base spec: 0.275W (55mA @ 5V). DisplayPort 1.2 provides 1.65W (500mA @ 3.3v).
Neither is sufficient to power the newest Chromecast dongle, but you can get far more juice out of a standard DP 1.2 port than you can from a standard HDMI port.
Neither is sufficient to power the newest Chromecast dongle, but you can get far more juice out of a standard DP 1.2 port than you can from a standard HDMI port.