Add setter for GrGLSLShaderVar layout qualifier

src/gpu/glsl/GrGLSLShaderVar.h

Index: src/gpu/glsl/GrGLSLShaderVar.h
diff --git a/src/gpu/glsl/GrGLSLShaderVar.h b/src/gpu/glsl/GrGLSLShaderVar.h
index a8a9a47ba203a12e1991f98a8a553e093f52d5fd..1aedb916613384cc24f4fa6f9f8c67444ed72825 100644
--- a/src/gpu/glsl/GrGLSLShaderVar.h
+++ b/src/gpu/glsl/GrGLSLShaderVar.h
@@ -130,6 +130,13 @@ public:
     }
 
     /**
+     * Set the layout qualifier
+     */
+    void setLayoutQualifier(const char* layoutQualifier) {
+        fLayoutQualifier = layoutQualifier;
+    }
+
+    /**
      * Write a declaration of this variable to out.
      */
     void appendDecl(const GrGLSLCaps* glslCaps, SkString* out) const {