Fix Lod0 texture functions that take a bias parameter.

Texture functions that are in a divergent path can still take a bias parameter.
Treat the bias parameter as an explicit lod. The logic behind this is that the
implicit lod is considerd to be 0 like with other Lod0 functions, and then the
bias is added to it.

BUG=angle:604

Change-Id: I2dbc309c497d37e960209f08849f9d2bc9e1fbcc
Reviewed-on: https://chromium-review.googlesource.com/194544
Tested-by: Nicolas Capens <nicolascapens@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
diff --git a/src/compiler/translator/OutputHLSL.h b/src/compiler/translator/OutputHLSL.h
index 283e217..5d66fc5 100644
--- a/src/compiler/translator/OutputHLSL.h
+++ b/src/compiler/translator/OutputHLSL.h
@@ -104,6 +104,7 @@
             BIAS,
             LOD,
             LOD0,
+            LOD0BIAS,
             SIZE,   // textureSize()
             FETCH,
             GRAD