Support writing interface blocks in OutputGLSL.

BUG=angleproject:882
BUG=angleproject:1149

Change-Id: Iea0b1d0bc586ec9517a06793386c91890b7a5115
Reviewed-on: https://chromium-review.googlesource.com/297086
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/compiler/translator/OutputGLSLBase.h b/src/compiler/translator/OutputGLSLBase.h
index 2b443af..fa57c74 100644
--- a/src/compiler/translator/OutputGLSLBase.h
+++ b/src/compiler/translator/OutputGLSLBase.h
@@ -66,6 +66,9 @@
     bool structDeclared(const TStructure *structure) const;
     void declareStruct(const TStructure *structure);
 
+    void declareInterfaceBlockLayout(const TInterfaceBlock *interfaceBlock);
+    void declareInterfaceBlock(const TInterfaceBlock *interfaceBlock);
+
     void writeBuiltInFunctionTriplet(Visit visit, const char *preStr, bool useEmulatedFunction);
 
     TInfoSinkBase &mObjSink;