Fix and enable warning C4244 (Conversion from 'type1' to 'type2', possible loss of data)

Change-Id: Id0e06d7d6600344d858f00dabc219d79289bbc82
Reviewed-on: https://chromium-review.googlesource.com/265020
Tested-by: Minmin Gong <mgong@microsoft.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/compiler/translator/InitializeVariables.cpp b/src/compiler/translator/InitializeVariables.cpp
index 0e3e2eb..2bb609a 100644
--- a/src/compiler/translator/InitializeVariables.cpp
+++ b/src/compiler/translator/InitializeVariables.cpp
@@ -13,7 +13,7 @@
 TIntermConstantUnion *constructFloatConstUnionNode(const TType &type)
 {
     TType myType = type;
-    unsigned char size = myType.getNominalSize();
+    unsigned char size = static_cast<unsigned char>(myType.getNominalSize());
     if (myType.isMatrix())
         size *= size;
     ConstantUnion *u = new ConstantUnion[size];