[DevTools] Do not allow Page.setDownloadBehavior for extensions

Bug: 866426
Change-Id: I71b672978e1a8ec779ede49da16b21198567d3a4
Reviewed-on: https://chromium-review.googlesource.com/c/1270007
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598004}
void RenderFrameDevToolsAgentHost::OnPageScaleFactorChanged(
    float page_scale_factor) {
  for (auto* input : protocol::InputHandler::ForAgentHost(this))
    input->OnPageScaleFactorChanged(page_scale_factor);
}

void RenderFrameDevToolsAgentHost::OnPageScaleFactorChanged(
    float page_scale_factor) {
  for (auto* input : protocol::InputHandler::ForAgentHost(this))
    input->OnPageScaleFactorChanged(page_scale_factor);
}
