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/ValidateGlobalInitializer.h b/src/compiler/translator/ValidateGlobalInitializer.h
index 28c005b..c3d2a47 100644
--- a/src/compiler/translator/ValidateGlobalInitializer.h
+++ b/src/compiler/translator/ValidateGlobalInitializer.h
@@ -8,7 +8,7 @@
 #define COMPILER_TRANSLATOR_VALIDATEGLOBALINITIALIZER_H_
 
 class TIntermTyped;
-struct TParseContext;
+class TParseContext;
 
 // Returns true if the initializer is valid.
 bool ValidateGlobalInitializer(TIntermTyped *initializer, const TParseContext *context, bool *warning);