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.h b/src/libANGLE/renderer/null/FramebufferNULL.h
index b0b5106..3975739 100644
--- a/src/libANGLE/renderer/null/FramebufferNULL.h
+++ b/src/libANGLE/renderer/null/FramebufferNULL.h
@@ -65,8 +65,8 @@
 
     bool checkStatus(const gl::Context *context) const override;
 
-    gl::Error syncState(const gl::Context *context,
-                        const gl::Framebuffer::DirtyBits &dirtyBits) override;
+    angle::Result syncState(const gl::Context *context,
+                            const gl::Framebuffer::DirtyBits &dirtyBits) override;
 
     gl::Error getSamplePosition(const gl::Context *context,
                                 size_t index,