Add shader translator support for OVR_multiview

The OVR_multiview and OVR_multiview2 extensions add gl_ViewID_OVR to
shaders. gl_ViewID_OVR can be translated either as is in GLSL output
or as a uniform by setting the SH_TRANSLATE_VIEWID_OVR_AS_UNIFORM
compiler flag.

If WebGL output is selected, the shaders will be validated according
to proposed rules in the WEBGL_multiview spec.

BUG=angleproject:1669
TEST=angle_unittests

Change-Id: I19ea3a6c8b4edb78be03f1a50a96bfef018870d0
Reviewed-on: https://chromium-review.googlesource.com/422848
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
diff --git a/src/compiler/translator/FindSymbolNode.cpp b/src/compiler/translator/FindSymbolNode.cpp
new file mode 100644
index 0000000..87fb9d5
--- /dev/null
+++ b/src/compiler/translator/FindSymbolNode.cpp
@@ -0,0 +1,58 @@
+//
+// Copyright (c) 2015 The ANGLE Project Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// FindSymbol.cpp:
+//     Utility for finding a symbol node inside an AST tree.
+
+#include "compiler/translator/FindSymbolNode.h"
+
+#include "compiler/translator/IntermNode.h"
+
+namespace sh
+{
+
+namespace
+{
+
+class SymbolFinder : public TIntermTraverser
+{
+  public:
+    SymbolFinder(const TString &symbolName, TBasicType basicType)
+        : TIntermTraverser(true, false, false),
+          mSymbolName(symbolName),
+          mNodeFound(nullptr),
+          mBasicType(basicType)
+    {
+    }
+
+    void visitSymbol(TIntermSymbol *node)
+    {
+        if (node->getBasicType() == mBasicType && node->getSymbol() == mSymbolName)
+        {
+            mNodeFound = node;
+        }
+    }
+
+    bool isFound() const { return mNodeFound != nullptr; }
+    const TIntermSymbol *getNode() const { return mNodeFound; }
+
+  private:
+    TString mSymbolName;
+    TIntermSymbol *mNodeFound;
+    TBasicType mBasicType;
+};
+
+}  // anonymous namespace
+
+const TIntermSymbol *FindSymbolNode(TIntermNode *root,
+                                    const TString &symbolName,
+                                    TBasicType basicType)
+{
+    SymbolFinder finder(symbolName, basicType);
+    root->traverse(&finder);
+    return finder.getNode();
+}
+
+}  // namespace sh