Enable drawBuffers() also on ES3

Source/modules/webgl/WebGLFramebuffer.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 587 matching lines @@
 {
     m_drawBuffers = bufs;
     m_filteredDrawBuffers.resize(m_drawBuffers.size());
     for (size_t i = 0; i < m_filteredDrawBuffers.size(); ++i)
         m_filteredDrawBuffers[i] = GL_NONE;
     drawBuffersIfNecessary(true);
 }
 
 void WebGLFramebuffer::drawBuffersIfNecessary(bool force)
 {
-    if (!context()->extensionEnabled(WebGLDrawBuffersName))
-        return;
-    bool reset = force;
-    // This filtering works around graphics driver bugs on Mac OS X.
-    for (size_t i = 0; i < m_drawBuffers.size(); ++i) {
-        if (m_drawBuffers[i] != GL_NONE && getAttachment(m_drawBuffers[i])) {
-            if (m_filteredDrawBuffers[i] != m_drawBuffers[i]) {
-                m_filteredDrawBuffers[i] = m_drawBuffers[i];
-                reset = true;
-            }
-        } else {
-            if (m_filteredDrawBuffers[i] != GL_NONE) {
-                m_filteredDrawBuffers[i] = GL_NONE;
-                reset = true;
+    if (context()->isWebGL2OrHigher()
+        || context()->extensionEnabled(WebGLDrawBuffersName)) {
+        bool reset = force;
+        // This filtering works around graphics driver bugs on Mac OS X.
+        for (size_t i = 0; i < m_drawBuffers.size(); ++i) {
+            if (m_drawBuffers[i] != GL_NONE && getAttachment(m_drawBuffers[i])) {
+                if (m_filteredDrawBuffers[i] != m_drawBuffers[i]) {
+                    m_filteredDrawBuffers[i] = m_drawBuffers[i];
+                    reset = true;
+                }
+            } else {
+                if (m_filteredDrawBuffers[i] != GL_NONE) {
+                    m_filteredDrawBuffers[i] = GL_NONE;
+                    reset = true;
+                }
             }
         }
-    }
-    if (reset) {
-        context()->webContext()->drawBuffersEXT(
-            m_filteredDrawBuffers.size(), m_filteredDrawBuffers.data());
+        if (reset) {
+            context()->webContext()->drawBuffersEXT(
+                m_filteredDrawBuffers.size(), m_filteredDrawBuffers.data());
+        }
     }
 }
 
 GLenum WebGLFramebuffer::getDrawBuffer(GLenum drawBuffer)
 {
     int index = static_cast<int>(drawBuffer - GL_DRAW_BUFFER0_EXT);
     ASSERT(index >= 0);
     if (index < static_cast<int>(m_drawBuffers.size()))
         return m_drawBuffers[index];
     if (drawBuffer == GL_DRAW_BUFFER0_EXT)
@@ skipping 15 matching lines @@
     return true;
 }
 
 DEFINE_TRACE(WebGLFramebuffer)
 {
     visitor->trace(m_attachments);
     WebGLContextObject::trace(visitor);
 }
 
 }