Fix OpenGL ES extension checks for floating point textures.
Fix OpenGL ES extension checks for floating point textures.

BUG=angleproject:1145
BUG=angleproject:884

Change-Id: I1ab16a187155573989f0605dbdd06f73ad8c8c58
Reviewed-on: https://chromium-review.googlesource.com/322691
Reviewed-by: Corentin Wallez <470c533e86f4f848c98c7e11fffc2d043494a401@chromium.org>
Tested-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>

mlfarrell/angle,ppy/angle,MSOpenTech/angle,MSOpenTech/angle,ecoal95/angle,domokit/waterfall,ecoal95/angle,ecoal95/angle,ppy/angle,mlfarrell/angle,mikolalysenko/angle,MSOpenTech/angle,mikolalysenko/angle,ecoal95/angle,ecoal95/angle,ppy/angle,mlfarrell/angle,mikolalysenko/angle,domokit/waterfall,MSOpenTech/angle,mlfarrell/angle,mikolalysenko/angle,ppy/angle