I believe we can use record<ByteString, ByteString> now.

We can. In fact, that was the original reason I set out to add record<> support to our WebIDL code :-) Before the code landed I sent https://codereview.chromium.org/2691513002/, I just never got around to updating it afterwards.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9e1372a28311ec4b7fee0ae76eba7301069e7c6a

commit 9e1372a28311ec4b7fee0ae76eba7301069e7c6a
Author: raphael.kubo.da.costa <raphael.kubo.da.costa@intel.com>
Date: Fri Apr 07 14:30:12 2017

bindings: Skip undefined property descriptors when creating records.

We were being too aggressive with our DCHECK(desc->IsObject()). The spec
says (and we even mention it in a comment) that a call to
Object.getOwnPropertyDescriptor can return undefined in addition to a proper
object descriptor.

We were only considering the latter case, and crashing on the DCHECK if we
ever received an undefined descriptor, which can happen when a Proxy is used
in JS.

This is also covered by external/wpt/fetch/api/headers/headers-record.html.

BUG= 707365 
R=bashi@chromium.org,haraken@chromium.org,yukishiino@chromium.org

Review-Url: https://codereview.chromium.org/2801003005
Cr-Commit-Position: refs/heads/master@{#462850}

[modify] https://crrev.com/9e1372a28311ec4b7fee0ae76eba7301069e7c6a/third_party/WebKit/LayoutTests/bindings/record-type.html
[modify] https://crrev.com/9e1372a28311ec4b7fee0ae76eba7301069e7c6a/third_party/WebKit/Source/bindings/core/v8/NativeValueTraitsImpl.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/07c092298a6243fc2c829e517cf2b19f4caea26c

commit 07c092298a6243fc2c829e517cf2b19f4caea26c
Author: raphael.kubo.da.costa <raphael.kubo.da.costa@intel.com>
Date: Tue Apr 11 14:35:07 2017

Fetch: Make Headers' constructor match the current spec IDL.

Instead of specifying several different constructors in the IDL (including
an overload for the defunct OpenEndedDictionary type), make Headers.idl
match the Fetch spec and just declare a single constructor that optionally
takes a HeadersInit type, which has also been modified to take a
record<ByteString,ByteString> instead of a Dictionary now that we support
records in the WebIDL compiler.

By using HeadersInit, which we define in the same IDL, we can get rid of
RequestInit::headers_dictionary altogether and leave most of the V8-Impl
type conversions to the auto-generated bindings code. Consequently, this
also lets us remove several Header::Create() overloads.

BUG= 707365 
R=tyoshino@chromium.org,yhirano@chromium.org

Review-Url: https://codereview.chromium.org/2691513002
Cr-Commit-Position: refs/heads/master@{#463623}

[modify] https://crrev.com/07c092298a6243fc2c829e517cf2b19f4caea26c/third_party/WebKit/LayoutTests/external/wpt/fetch/api/headers/headers-basic-expected.txt
[modify] https://crrev.com/07c092298a6243fc2c829e517cf2b19f4caea26c/third_party/WebKit/LayoutTests/external/wpt/fetch/api/headers/headers-record-expected.txt
[modify] https://crrev.com/07c092298a6243fc2c829e517cf2b19f4caea26c/third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/request.js
[modify] https://crrev.com/07c092298a6243fc2c829e517cf2b19f4caea26c/third_party/WebKit/Source/bindings/modules/v8/generated.gni
[modify] https://crrev.com/07c092298a6243fc2c829e517cf2b19f4caea26c/third_party/WebKit/Source/modules/fetch/Headers.cpp
[modify] https://crrev.com/07c092298a6243fc2c829e517cf2b19f4caea26c/third_party/WebKit/Source/modules/fetch/Headers.h
[modify] https://crrev.com/07c092298a6243fc2c829e517cf2b19f4caea26c/third_party/WebKit/Source/modules/fetch/Headers.idl
[modify] https://crrev.com/07c092298a6243fc2c829e517cf2b19f4caea26c/third_party/WebKit/Source/modules/fetch/Request.cpp
[modify] https://crrev.com/07c092298a6243fc2c829e517cf2b19f4caea26c/third_party/WebKit/Source/modules/fetch/RequestInit.cpp
[modify] https://crrev.com/07c092298a6243fc2c829e517cf2b19f4caea26c/third_party/WebKit/Source/modules/fetch/RequestInit.h
[modify] https://crrev.com/07c092298a6243fc2c829e517cf2b19f4caea26c/third_party/WebKit/Source/modules/fetch/Response.cpp
[modify] https://crrev.com/07c092298a6243fc2c829e517cf2b19f4caea26c/third_party/WebKit/Source/modules/fetch/ResponseInit.idl