Move variable identifier parsing to ParseContext

This change is purely refactoring existing functionality to make it
easier to change variable identifier parsing.

BUG=angleproject:911
BUG=541551

Change-Id: I282fbb66d40cd71fa0f4804e4a8e893744cd6bfc
Reviewed-on: https://chromium-review.googlesource.com/309724
Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/compiler/translator/ParseContext.h b/src/compiler/translator/ParseContext.h
index cb73fd9..3b02fa2 100644
--- a/src/compiler/translator/ParseContext.h
+++ b/src/compiler/translator/ParseContext.h
@@ -115,6 +115,9 @@
 
     // This method is guaranteed to succeed, even if no variable with 'name' exists.
     const TVariable *getNamedVariable(const TSourceLoc &location, const TString *name, const TSymbol *symbol);
+    TIntermTyped *parseVariableIdentifier(const TSourceLoc &location,
+                                          const TString *name,
+                                          const TSymbol *symbol);
 
     bool parseVectorFields(const TString&, int vecSize, TVectorFields&, const TSourceLoc &line);