Add a helper method to parse invariant declarations.

This pulls out more functionality from the grammar into simple
c++ source files.

BUG=angle:711

Change-Id: I19121d710dc1543585361cb53a0deb2ea0479db9
Reviewed-on: https://chromium-review.googlesource.com/212938
Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Nicolas Capens <capn@chromium.org>
diff --git a/src/compiler/translator/ParseContext.h b/src/compiler/translator/ParseContext.h
index 3da9420..1f4cbde 100644
--- a/src/compiler/translator/ParseContext.h
+++ b/src/compiler/translator/ParseContext.h
@@ -129,6 +129,8 @@
     TIntermAggregate* parseSingleDeclaration(TPublicType &publicType, const TSourceLoc& identifierLocation, const TString &identifier);
     TIntermAggregate* parseSingleArrayDeclaration(TPublicType &publicType, const TSourceLoc& identifierLocation, const TString &identifier, const TSourceLoc& indexLocation, TIntermTyped *indexExpression);
     TIntermAggregate* parseSingleInitDeclaration(TPublicType &publicType, const TSourceLoc& identifierLocation, const TString &identifier, const TSourceLoc& initLocation, TIntermTyped *initializer);
+    TIntermAggregate* parseInvariantDeclaration(const TSourceLoc &invariantLoc, const TSourceLoc &identifierLoc, const TString *identifier, const TSymbol *symbol);
+
     TIntermAggregate* parseDeclarator(TPublicType &publicType, TIntermAggregate *aggregateDeclaration, TSymbol *identifierSymbol, const TSourceLoc& identifierLocation, const TString &identifier);
     TIntermAggregate* parseArrayDeclarator(TPublicType &publicType, const TSourceLoc& identifierLocation, const TString &identifier, const TSourceLoc& arrayLocation, TIntermNode *declaratorList, TIntermTyped *indexExpression);
     TIntermAggregate* parseInitDeclarator(TPublicType &publicType, TIntermAggregate *declaratorList, const TSourceLoc& identifierLocation, const TString &identifier, const TSourceLoc& initLocation, TIntermTyped *initializer);