Run clang-tidy modernize-use-equals-{delete,default} on //printing

See the bugs and cxx post for justification and details:
https://groups.google.com/a/chromium.org/forum/#!topic/cxx/RkOHzIK6Tq8

This change was done using clang-tidy as described here:
https://chromium.googlesource.com/chromium/src/+/lkcr/docs/clang_tidy.md

In some cases the the tool leaves behind a string of commas where it
replaced a member initializer list
(https://bugs.llvm.org/show_bug.cgi?id=35051). They were cleaned up with:
  git diff --name-only | \
    xargs sed -E -i 's/(^\s*|\)\s*):[ ,]*= default/\1 = default/'

BUG=778959,778957

Change-Id: Id32fe134ba35b64c9593c46297620e84e508d1ce
Reviewed-on: https://chromium-review.googlesource.com/789727
Reviewed-by: Rebekah Potter <[email protected]>
Commit-Queue: Chris Watkins <[email protected]>
Cr-Commit-Position: refs/heads/master@{#520864}
diff --git a/printing/page_setup.cc b/printing/page_setup.cc
index 69442b0..fb342d5 100644
--- a/printing/page_setup.cc
+++ b/printing/page_setup.cc
@@ -43,7 +43,7 @@
 
 PageSetup::PageSetup(const PageSetup& other) = default;
 
-PageSetup::~PageSetup() {}
+PageSetup::~PageSetup() = default;
 
 void PageSetup::Clear() {
   physical_size_.SetSize(0, 0);