Run clang-tidy modernize-use-equals-{delete,default} on //net, pt 2

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
This CL was uploaded by git cl split.

R=eroman@chromium.org

Change-Id: I0c2a41fbeee3648e886b70f259e333176ffa4334
Reviewed-on: https://chromium-review.googlesource.com/799595
Reviewed-by: Eric Roman <eroman@chromium.org>
Commit-Queue: Chris Watkins <watk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520798}

diff --git a/net/http/partial_data.cc b/net/http/partial_data.cc
index dceea25b..7243fcf 100644
--- a/net/http/partial_data.cc
+++ b/net/http/partial_data.cc

@@ -43,8 +43,7 @@
       weak_factory_(this) {
 }
 
-PartialData::~PartialData() {
-}
+PartialData::~PartialData() = default;
 
 bool PartialData::Init(const HttpRequestHeaders& headers) {
   std::string range_header;