The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/93457c2766b87bb015e124db70f24f786c73b3a7

commit 93457c2766b87bb015e124db70f24f786c73b3a7
Author: wutao <wutao@chromium.org>
Date: Tue Dec 11 17:27:34 2018

app_list: Remove flag kEnableContinueReading

This feature has been enabled by default since M70 and stable enough to
be always on.

Bug:  913694 
Test: manual and coverred by unittest
Change-Id: Ice7240c8d47e45b89324c85de85d398dc9233df8
Reviewed-on: https://chromium-review.googlesource.com/c/1371066
Commit-Queue: Tao Wu <wutao@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615568}
[modify] https://crrev.com/93457c2766b87bb015e124db70f24f786c73b3a7/ash/public/cpp/app_list/app_list_features.cc
[modify] https://crrev.com/93457c2766b87bb015e124db70f24f786c73b3a7/ash/public/cpp/app_list/app_list_features.h
[modify] https://crrev.com/93457c2766b87bb015e124db70f24f786c73b3a7/chrome/browser/about_flags.cc
[modify] https://crrev.com/93457c2766b87bb015e124db70f24f786c73b3a7/chrome/browser/flag_descriptions.cc
[modify] https://crrev.com/93457c2766b87bb015e124db70f24f786c73b3a7/chrome/browser/flag_descriptions.h
[modify] https://crrev.com/93457c2766b87bb015e124db70f24f786c73b3a7/chrome/browser/ui/app_list/search/app_search_provider.cc
[modify] https://crrev.com/93457c2766b87bb015e124db70f24f786c73b3a7/chrome/browser/ui/app_list/search/tests/app_search_provider_unittest.cc