Move OutputHLSL utility methods to other files.

OutputHLSL was become a large, unweildy file. Some were also useful
to other classes, even on the GL back-end, but were inacessible.

Refactoring patch only.

BUG=angle:466

Change-Id: Id216147122ca105c6ccdf0ba0c5f6c5038726965
Reviewed-on: https://chromium-review.googlesource.com/203459
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Nicolas Capens <nicolascapens@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libGLESv2/DynamicHLSL.cpp b/src/libGLESv2/DynamicHLSL.cpp
index 935d841..507cf81 100644
--- a/src/libGLESv2/DynamicHLSL.cpp
+++ b/src/libGLESv2/DynamicHLSL.cpp
@@ -1034,7 +1034,7 @@
 // This method needs to match OutputHLSL::decorate
 std::string DynamicHLSL::decorateVariable(const std::string &name)
 {
-    if (name.compare(0, 3, "gl_") != 0 && name.compare(0, 3, "dx_") != 0)
+    if (name.compare(0, 3, "gl_"))
     {
         return "_" + name;
     }