Avoid copy of PixelUnpackState in Texture::setImage.
Avoid copy of PixelUnpackState in Texture::setImage.

The ternary operator determines that the common type is the value type, causing
a copy of PixelUnpackState.  If PixelUnpackState::pixelBuffer is non-null then
there is an assertion failure in the destructor on any call to Texture::setImage.

See:http://stackoverflow.com/a/30088030

BUG=angleproject:1149

Change-Id: I9654e65956339d6b6966ad65a98cf37ad4e00452
Reviewed-on: https://chromium-review.googlesource.com/297084
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>
Reviewed-by: Corentin Wallez <470c533e86f4f848c98c7e11fffc2d043494a401@chromium.org>
Tested-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>

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