More shader refactor cleanup

Removed VertexShader and FragmentShader in favor of using a single Shader object
Used VertexShaderD3D and FragmentShaderD3D directly when appropriate.

BUG=angle:731
Change-Id: Ib1ffdf85ee0bfa7c88bb9ddb1029ccbd63a9dbe1
Reviewed-on: https://chromium-review.googlesource.com/213840
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Brandon Jones <bajones@chromium.org>
diff --git a/src/libGLESv2/Program.h b/src/libGLESv2/Program.h
index 777e386..7e84859 100644
--- a/src/libGLESv2/Program.h
+++ b/src/libGLESv2/Program.h
@@ -26,8 +26,6 @@
 namespace gl
 {
 class ResourceManager;
-class FragmentShader;
-class VertexShader;
 class Shader;
 
 extern const char * const g_fakepath;
@@ -121,8 +119,8 @@
     void unlink(bool destroy = false);
     void resetUniformBlockBindings();
 
-    FragmentShader *mFragmentShader;
-    VertexShader *mVertexShader;
+    Shader *mFragmentShader;
+    Shader *mVertexShader;
 
     AttributeBindings mAttributeBindings;