Do not hash mapping field names of a reserved struct.

With this fixed, Chrome behaves the same on WebGL conformance tests 1.0.2 with/without --enable-shader-name-hashing

BUG=
TEST=WebGL conformance tests
Review URL: https://codereview.appspot.com/7229043

git-svn-id: https://angleproject.googlecode.com/svn/branches/dx11proto@1817 736b8ea6-26fd-11df-bfd4-992fa37f6226
diff --git a/src/compiler/OutputGLSLBase.cpp b/src/compiler/OutputGLSLBase.cpp
index 45fabed..1b9a10d 100644
--- a/src/compiler/OutputGLSLBase.cpp
+++ b/src/compiler/OutputGLSLBase.cpp
@@ -262,7 +262,13 @@
             {
                 out << ".";
                 // TODO(alokp): ASSERT
-                out << hashName(node->getType().getFieldName());
+                TString fieldName = node->getType().getFieldName();
+
+                const TType& structType = node->getLeft()->getType();
+                if (!mSymbolTable.findBuiltIn(structType.getTypeName()))
+                    fieldName = hashName(fieldName);
+
+                out << fieldName;
                 visitChildren = false;
             }
             break;