Rename ConstantUnion to TConstantUnion.

This clarified that we're using the Pool allocator/deallocator for
this type.

BUG=angleproject:993

Change-Id: If8c95f6054d07291e7014be0d4e35766ba2e943b
Reviewed-on: https://chromium-review.googlesource.com/269131
Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
diff --git a/src/compiler/translator/Intermediate.cpp b/src/compiler/translator/Intermediate.cpp
index ebe6c39..81f8aa0 100644
--- a/src/compiler/translator/Intermediate.cpp
+++ b/src/compiler/translator/Intermediate.cpp
@@ -361,7 +361,7 @@
 //
 
 TIntermConstantUnion *TIntermediate::addConstantUnion(
-    ConstantUnion *unionArrayPointer, const TType &t, const TSourceLoc &line)
+    TConstantUnion *unionArrayPointer, const TType &t, const TSourceLoc &line)
 {
     TIntermConstantUnion *node = new TIntermConstantUnion(unionArrayPointer, t);
     node->setLine(line);
@@ -378,11 +378,11 @@
     node->setLine(line);
     TIntermConstantUnion *constIntNode;
     TIntermSequence *sequenceVector = node->getSequence();
-    ConstantUnion *unionArray;
+    TConstantUnion *unionArray;
 
     for (int i = 0; i < fields.num; i++)
     {
-        unionArray = new ConstantUnion[1];
+        unionArray = new TConstantUnion[1];
         unionArray->setIConst(fields.offsets[i]);
         constIntNode = addConstantUnion(
             unionArray, TType(EbtInt, EbpUndefined, EvqConst), line);