Limit foreign fetch to only intercept requests made from secure contexts.

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index e01306b0e421bdcee5d147f4d81dbb7d464c3fd0..8b43e824f6c89f4e6b9af0ec440274c6376fb9ea 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -3913,6 +3913,9 @@ void RenderFrameImpl::willSendRequest(
     extra_data->set_lofi_state(navigation_state->common_params().lofi_state);
   else
     extra_data->set_lofi_state(is_using_lofi_ ? LOFI_ON : LOFI_OFF);
+  WebString error;
+  extra_data->set_initiated_in_secure_context(
+      frame->document().isSecureContext(error));
   request.setExtraData(extra_data);
 
   // TODO(creis): Update prefetching to work with out-of-process iframes.