Implement EXT_shader_texture_lod

BUG=angle:551

Change-Id: I81d7574a15861f1b24ddf6147cf71adbf20e10f3
Reviewed-on: https://chromium-review.googlesource.com/194960
Tested-by: Nicolas Capens <nicolascapens@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
diff --git a/src/compiler/translator/OutputGLSLBase.cpp b/src/compiler/translator/OutputGLSLBase.cpp
index 816850e..55238c8 100644
--- a/src/compiler/translator/OutputGLSLBase.cpp
+++ b/src/compiler/translator/OutputGLSLBase.cpp
@@ -801,7 +801,9 @@
 {
     TString name = TFunction::unmangleName(mangled_name);
     if (mSymbolTable.findBuiltIn(mangled_name, mShaderVersion) != NULL || name == "main")
-        return name;
+    {
+        return translateTextureFunction(name);
+    }
     return hashName(name);
 }