Make TParseContext a class, with private data.

*re-land with build fix*

BUG=angleproject:995

Change-Id: I67d3ded8f6c705b54fb372857e07ce1a86b58475
Reviewed-on: https://chromium-review.googlesource.com/271162
Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
diff --git a/src/compiler/translator/ValidateSwitch.h b/src/compiler/translator/ValidateSwitch.h
index 88b68a5..ddbefc5 100644
--- a/src/compiler/translator/ValidateSwitch.h
+++ b/src/compiler/translator/ValidateSwitch.h
@@ -9,7 +9,7 @@
 
 #include "compiler/translator/IntermNode.h"
 
-struct TParseContext;
+class TParseContext;
 
 class ValidateSwitch : public TIntermTraverser
 {