Optimize ShaderVariable::isBuiltIn.

This makes the check a bit faster, by inlining the prefix check.
Also some cleanups to ValidateVertexShaderAttributeTypeMatch.

BUG=angleproject:2202

Change-Id: Ifeab4cd85a91a1639a461f44776a68ac98c5bd79
Reviewed-on: https://chromium-review.googlesource.com/761240
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/State.cpp b/src/libANGLE/State.cpp
index 1ceed3f..489bd72 100644
--- a/src/libANGLE/State.cpp
+++ b/src/libANGLE/State.cpp
@@ -1403,6 +1403,11 @@
     return mVertexAttribCurrentValues[attribNum];
 }
 
+const std::vector<VertexAttribCurrentValueData> &State::getVertexAttribCurrentValues() const
+{
+    return mVertexAttribCurrentValues;
+}
+
 const void *State::getVertexAttribPointer(unsigned int attribNum) const
 {
     return getVertexArray()->getVertexAttribute(attribNum).pointer;