Fix base level for generateMipmap in blink

Source/modules/webgl/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 2363 matching lines @@
 }
 
 void WebGLRenderingContextBase::generateMipmap(GLenum target)
 {
     if (isContextLost())
         return;
     WebGLTexture* tex = validateTextureBinding("generateMipmap", target, false);
     if (!tex)
         return;
     if (!tex->canGenerateMipmaps()) {
-        synthesizeGLError(GL_INVALID_OPERATION, "generateMipmap", "level 0 not power of 2 or not all the same size");
+        synthesizeGLError(GL_INVALID_OPERATION, "generateMipmap", "cannot generate mipmaps");
         return;
     }
     if (tex->getInternalFormat(target, 0) == GL_SRGB_EXT || tex->getInternalFormat(target, 0) == GL_SRGB_ALPHA_EXT) {
         synthesizeGLError(GL_INVALID_OPERATION, "generateMipmap", "cannot generate mipmaps for sRGB textures");
         return;
     }
     if (!validateSettableTexFormat("generateMipmap", tex->getInternalFormat(target, 0)))
         return;
 
     // generateMipmap won't work properly if minFilter is not NEAREST_MIPMAP_LINEAR
@@ skipping 4334 matching lines @@
 
     return totalBytesPerPixel;
 }
 
 DrawingBuffer* WebGLRenderingContextBase::drawingBuffer() const
 {
     return m_drawingBuffer.get();
 }
 
 } // namespace blink