Implement ES2 backend for Angle translator.

With this CL, we have the option to select a code output backend: GLSL, GLSL ES, or HLSL.

Note that we always emit the highest supported float precision for fragment shader due to anglebug 168.  Although this is a temporary solution, it's not against GLSL ES spec, because it's ok for implementation to upgrade precision.

Tested with WebGL conformance test suite, GLES2 conformance test suite (only failed 2/1198), and a few webgl demos, including worlds of webgl, aquarium, etc.

anglebug=81
test=translator emitting correct GLSL ES code when ES2 backend is selected.
Review URL: http://codereview.appspot.com/4550129

git-svn-id: https://angleproject.googlecode.com/svn/trunk@687 736b8ea6-26fd-11df-bfd4-992fa37f6226
diff --git a/src/compiler/OutputGLSLBase.h b/src/compiler/OutputGLSLBase.h
new file mode 100644
index 0000000..efd0b5f
--- /dev/null
+++ b/src/compiler/OutputGLSLBase.h
@@ -0,0 +1,53 @@
+//
+// Copyright (c) 2002-2011 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.
+//
+
+#ifndef CROSSCOMPILERGLSL_OUTPUTGLSLBASE_H_
+#define CROSSCOMPILERGLSL_OUTPUTGLSLBASE_H_
+
+#include <set>
+
+#include "compiler/ForLoopUnroll.h"
+#include "compiler/intermediate.h"
+#include "compiler/ParseHelper.h"
+
+class TOutputGLSLBase : public TIntermTraverser
+{
+public:
+    TOutputGLSLBase(TInfoSinkBase& objSink);
+
+protected:
+    TInfoSinkBase& objSink() { return mObjSink; }
+    void writeTriplet(Visit visit, const char* preStr, const char* inStr, const char* postStr);
+    void writeVariableType(const TType& type);
+    virtual bool writeVariablePrecision(TPrecision precision) = 0;
+    void writeFunctionParameters(const TIntermSequence& args);
+    const ConstantUnion* writeConstantUnion(const TType& type, const ConstantUnion* pConstUnion);
+
+    virtual void visitSymbol(TIntermSymbol* node);
+    virtual void visitConstantUnion(TIntermConstantUnion* node);
+    virtual bool visitBinary(Visit visit, TIntermBinary* node);
+    virtual bool visitUnary(Visit visit, TIntermUnary* node);
+    virtual bool visitSelection(Visit visit, TIntermSelection* node);
+    virtual bool visitAggregate(Visit visit, TIntermAggregate* node);
+    virtual bool visitLoop(Visit visit, TIntermLoop* node);
+    virtual bool visitBranch(Visit visit, TIntermBranch* node);
+
+    void visitCodeBlock(TIntermNode* node);
+
+private:
+    TInfoSinkBase& mObjSink;
+    bool mDeclaringVariables;
+
+    // Structs are declared as the tree is traversed. This set contains all
+    // the structs already declared. It is maintained so that a struct is
+    // declared only once.
+    typedef std::set<TString> DeclaredStructs;
+    DeclaredStructs mDeclaredStructs;
+
+    ForLoopUnroll mLoopUnroll;
+};
+
+#endif  // CROSSCOMPILERGLSL_OUTPUTGLSLBASE_H_