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/VertexArray.cpp b/src/libANGLE/VertexArray.cpp
index ca40a96..ac3a4b5 100644
--- a/src/libANGLE/VertexArray.cpp
+++ b/src/libANGLE/VertexArray.cpp
@@ -377,7 +377,7 @@
     mDirtyBits.set(DIRTY_BIT_ELEMENT_ARRAY_BUFFER);
 }
 
-gl::Error VertexArray::syncState(const Context *context)
+angle::Result VertexArray::syncState(const Context *context)
 {
     if (mDirtyBits.any())
     {
@@ -394,7 +394,7 @@
         memset(&mDirtyAttribBits, 0, sizeof(mDirtyAttribBits));
         memset(&mDirtyBindingBits, 0, sizeof(mDirtyBindingBits));
     }
-    return gl::NoError();
+    return angle::Result::Continue();
 }
 
 void VertexArray::onBindingChanged(const Context *context, int incr)