Framebuffer clear() needs to consider the situation some draw buffers are disabled.

This is when we expose DrawBuffers extension.

BUG=376951
TEST=the attached test case, webgl conformance
R=kbr@chromium.org,bajones@chromium.org

Review URL: https://codereview.chromium.org/315283002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@275338 0039d316-1c4b-4281-b951-d872f2087c98
void GLES2DecoderImpl::DoGetTexParameterfv(
    GLenum target, GLenum pname, GLfloat* params) {
  InitTextureMaxAnisotropyIfNeeded(target, pname);
  glGetTexParameterfv(target, pname, params);
}

void GLES2DecoderImpl::DoGetTexParameterfv(
    GLenum target, GLenum pname, GLfloat* params) {
  InitTextureMaxAnisotropyIfNeeded(target, pname);
  glGetTexParameterfv(target, pname, params);
}
