Always write data to new buffer in SimulateAttrib0

This is to work around linux nvidia driver bug.

TEST=asan
BUG=118970


Review URL: http://codereview.chromium.org/10019003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@131538 0039d316-1c4b-4281-b951-d872f2087c98
GLenum GLES2DecoderImpl::GetBoundReadFrameBufferInternalFormat() {
  FramebufferManager::FramebufferInfo* framebuffer =
      GetFramebufferInfoForTarget(GL_READ_FRAMEBUFFER);
  if (framebuffer != NULL) {
    return framebuffer->GetColorAttachmentFormat();
  } else if (offscreen_target_frame_buffer_.get()) {
    return offscreen_target_color_format_;
  } else {
    return back_buffer_color_format_;
  }
}

GLenum GLES2DecoderImpl::GetBoundReadFrameBufferInternalFormat() {
  FramebufferManager::FramebufferInfo* framebuffer =
      GetFramebufferInfoForTarget(GL_READ_FRAMEBUFFER);
  if (framebuffer != NULL) {
    return framebuffer->GetColorAttachmentFormat();
  } else if (offscreen_target_frame_buffer_.get()) {
    return offscreen_target_color_format_;
  } else {
    return back_buffer_color_format_;
  }
}
