gid="sth" get lost if rasterized=True is set in hexbin #2816
Description
Fragment below will write id="element" into the svg
plt.hexbin(x,y, cmap=plt.cm.YlOrRd_r,gid="element")
plt.savefig("img.svg")
which is as we could expect, but
plt.hexbin(x,y, cmap=plt.cm.YlOrRd_r,gid="element",rasterized=True)
plt.savefig("img.svg")
results in <image tag with different id (something like id="image9f9a4ebdcc")
(i am submitting new issue as tcaswell@stackoverflow suggested