Spare a thought for the poor souls who picked the bottom of the sixth inning of Friday’s series opener between the Mariners and Rangers to take a Safeco Field bathroom break — though, given the part of the Seattle order due up, they probably should have known better. Two big swings from Nelson Cruz and Robinson Cano in consecutive at-bats off Texas starter Cole Hamels flipped a one-run deficit into a narrow lead and provided the game’s decisive highlights. That support was enough for Seattle righty Hisashi Iwakuma, who settled in after an uneven start. And the slender advantage even survived the nightly bullpen tightrope walk, as Seattle edged the Rangers 4-3 in front of an announced Friday night crowd of 29,320. Cruz and Cano, back-to-back, just like you dreamed it up during spring training. “We joke about that,” Cruz said afterward. “Finally, we got something good. One and two. That was nice.” Iwakuma was tagged with three earned runs, none of which were really his fault. In the top of the second, left fielder Mark Trumbo got a late jump on Bobby Wilson’s two-out line drive that landed just beyond his dive and plated a pair of Rangers. In the fourth, Mitch Moreland reached base via a seeing-eye-single that second baseman Robinson Cano really should have gloved. Josh Hamilton then took advantage of Trumbo’s indirect route to the ball. Moreland later scored on an Iwakuma wild pitch.