Make WebGLRenderingContext.getSupportedExtensions() return type nullable

Source/core/html/canvas/WebGLRenderingContextBase.cpp

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 2582 matching lines @@
 
 String WebGLRenderingContextBase::getShaderSource(WebGLShader* shader)
 {
     if (isContextLost())
         return String();
     if (!validateWebGLObject("getShaderSource", shader))
         return "";
     return ensureNotNull(shader->source());
 }
 
-Vector<String> WebGLRenderingContextBase::getSupportedExtensions()
+Nullable<Vector<String> > WebGLRenderingContextBase::getSupportedExtensions()
 {
+    if (isContextLost())
+        return Nullable<Vector<String> >();
+
     Vector<String> result;
-    if (isContextLost())
-        return result;
 
     for (size_t i = 0; i < m_extensions.size(); ++i) {
         ExtensionTracker* tracker = m_extensions[i];
         if (extensionSupportedAndAllowed(tracker)) {
             const char* const* prefixes = tracker->prefixes();
             for (; *prefixes; ++prefixes) {
                 String prefixedName = String(*prefixes) + tracker->extensionName();
                 result.append(prefixedName);
             }
         }
@@ skipping 3076 matching lines @@
         if (m_textureUnits[i].m_texture2DBinding
             || m_textureUnits[i].m_textureCubeMapBinding) {
             m_onePlusMaxNonDefaultTextureUnit = i + 1;
             return;
         }
     }
     m_onePlusMaxNonDefaultTextureUnit = 0;
 }
 
 } // namespace WebCore