Use angle::Result in front-end. (Part 1)

This covers most of the hot paths used in draw calls. Gives in the
order of a 5% reduction in draw call overhead.

Bug: angleproject:2491
Change-Id: I2d53afb1163eaceed61fb9cd9ce6c1267c85c0fa
Reviewed-on: https://chromium-review.googlesource.com/c/1258149
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/renderer/null/FramebufferNULL.cpp b/src/libANGLE/renderer/null/FramebufferNULL.cpp
index b6c1bab..f6eeeaa 100644
--- a/src/libANGLE/renderer/null/FramebufferNULL.cpp
+++ b/src/libANGLE/renderer/null/FramebufferNULL.cpp
@@ -188,10 +188,10 @@
     return true;
 }
 
-gl::Error FramebufferNULL::syncState(const gl::Context *context,
-                                     const gl::Framebuffer::DirtyBits &dirtyBits)
+angle::Result FramebufferNULL::syncState(const gl::Context *context,
+                                         const gl::Framebuffer::DirtyBits &dirtyBits)
 {
-    return gl::NoError();
+    return angle::Result::Continue();
 }
 
 gl::Error FramebufferNULL::getSamplePosition(const gl::Context *context,