Roll gn 157d5de447..f3a5b8c1f9 (r514519:r520777)

  7f86d891eda0 gn: Check if formatting a single line list to multiple reduces penalty
  5accd24a5417 Remove base::SizeToToString[16]
  8f449e3d6a1f gn: Fix formatting of file containing only 2 block comments
  e643f226b1b9 add jumbo support when building gn itself
  e4963ba3016a Run clang-tidy modernize-use-equals-{delete,default} on //tools
  5eea716fd5c7 GN: Fix references to lib_[dir_]prefix, which should be lib_[dir_]switch
  8b6898fe4eaa Add option to gn bootstrap to specify the build directory
  3667991ece7e Use std::make_unique in GN code.
  e953738ca60c Clarify GN nonfatal unused build arg messages.
  e03b10a94417 Remove unneeded extern keywords in tools/gn.
  976fe5f366eb Add observer_list_threadsafe.cc to gn bootstrap deps
  36d1a861ddf1 [CFI] Add protected memory container class

TBR=dpranke@chromium.org

Change-Id: Id234a8f59a133da5a9f9158b87ac74430fa4179f