Fix a semantic index not being written for gl_FragCoord.

BUG=angle:608

Change-Id: Iebf7577a7a0c54cef25cfa7706840e8ad26b7a08
Reviewed-on: https://chromium-review.googlesource.com/195163
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Nicolas Capens <nicolascapens@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libGLESv2/DynamicHLSL.cpp b/src/libGLESv2/DynamicHLSL.cpp
index 9b47b4e..12a1ed9 100644
--- a/src/libGLESv2/DynamicHLSL.cpp
+++ b/src/libGLESv2/DynamicHLSL.cpp
@@ -639,7 +639,7 @@
 
     if (fragmentShader->mUsesFragCoord)
     {
-        pixelHLSL += "    float4 gl_FragCoord : " + fragCoordSemantic + ";\n";
+        pixelHLSL += "    float4 gl_FragCoord : " + fragCoordSemantic + Str(fragCoordSemanticIndex) + ";\n";
     }
 
     if (fragmentShader->mUsesPointCoord && shaderModel >= 3)