Move LinkResult to the gl:: namespace.

This is a derived type from gl::Error so makes sense to be there.
Also makes it more accessible than in ProgramImpl.h

BUG=angleproject:1897

Change-Id: Id41b13e5a072745d8c361057f5bef8f152e0452b
Reviewed-on: https://chromium-review.googlesource.com/522872
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/renderer/null/ProgramNULL.h b/src/libANGLE/renderer/null/ProgramNULL.h
index 2be4b30..9b6fda3 100644
--- a/src/libANGLE/renderer/null/ProgramNULL.h
+++ b/src/libANGLE/renderer/null/ProgramNULL.h
@@ -21,16 +21,16 @@
     ProgramNULL(const gl::ProgramState &state);
     ~ProgramNULL() override;
 
-    LinkResult load(const gl::Context *context,
-                    gl::InfoLog &infoLog,
-                    gl::BinaryInputStream *stream) override;
+    gl::LinkResult load(const gl::Context *context,
+                        gl::InfoLog &infoLog,
+                        gl::BinaryInputStream *stream) override;
     void save(gl::BinaryOutputStream *stream) override;
     void setBinaryRetrievableHint(bool retrievable) override;
     void setSeparable(bool separable) override;
 
-    LinkResult link(const gl::Context *context,
-                    const gl::VaryingPacking &packing,
-                    gl::InfoLog &infoLog) override;
+    gl::LinkResult link(const gl::Context *context,
+                        const gl::VaryingPacking &packing,
+                        gl::InfoLog &infoLog) override;
     GLboolean validate(const gl::Caps &caps, gl::InfoLog *infoLog) override;
 
     void setUniform1fv(GLint location, GLsizei count, const GLfloat *v) override;