Use glGetStringi to get extensions when available.

include/gpu/gl/GrGLExtensions.h

Index: include/gpu/gl/GrGLExtensions.h
===================================================================
--- include/gpu/gl/GrGLExtensions.h	(revision 0)
+++ include/gpu/gl/GrGLExtensions.h	(revision 0)
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrGLExtensions_DEFINED
+#define GrGLExtensions_DEFINED
+
+#include "GrGLInterface.h"
+#include "SkString.h"
+#include "SkTArray.h"
+
+/**
+ * This helper queries the current GL context for its extensions, remembers them, and can be
+ * queried. It supports both glGetString- and glGetStringi-style extension string APIs and will
+ * use the latter if it is available.
+ */
+class GrGLExtensions {
+public:
+    bool init(GrGLBinding binding, const GrGLInterface* iface) {
+        GrAssert(binding & iface->fBindingsExported);
+        return this->init(binding, iface->fGetString, iface->fGetStringi, iface->fGetIntegerv);
+    }
+    /**
+     * We sometimes need to use this class without having yet created a GrGLInterface. This version
+     * of init expects that getString is always non-NULL while getIntegerv and getStringi are non-
+     * NULL if on desktop GL with version 3.0 or higher. Otherwise it will fail.
+     */
+    bool init(GrGLBinding binding,
+              GrGLGetStringProc getString,
+              GrGLGetStringiProc getStringi,
+              GrGLGetIntegervProc getIntegerv);
+    
+    /**
+     * Queries whether an extension is present. This will fail if init() has not been called.
+     */
+    bool has(const char*) const;
+    
+    void reset() { fStrings.reset(); }
+
+private:
+    SkTArray<SkString> fStrings;
+};
+
+#endif