Add DisplayPlacement/Layout mojoms + StructTraits.

ui/display/display_layout.cc

Index: ui/display/display_layout.cc
diff --git a/ui/display/display_layout.cc b/ui/display/display_layout.cc
index 9b5ee1763f6263991c161e9c4ab592b8a468c41f..d6d843f99a95103cf9b5926ea468d817e924d267 100644
--- a/ui/display/display_layout.cc
+++ b/ui/display/display_layout.cc
@@ -353,6 +353,18 @@ DisplayPlacement::DisplayPlacement(const DisplayPlacement& placement)
       offset(placement.offset),
       offset_reference(placement.offset_reference) {}
 
+bool DisplayPlacement::operator==(const DisplayPlacement& other) const {
+  return display_id == other.display_id &&                //

[Daniel Erat, 2017/02/01 23:06:37]

what are all these empty trailing comments for?

[kylechar, 2017/02/02 14:40:48]

Just to keep the statements one per line after running 'git cl format'.

It feels easier to read with one == per line and easier to see if someone adds a
member without updating the operator==. I can remove the comments if you don't
feel it's necessary.

[Daniel Erat, 2017/02/02 16:55:13]

ah, i didn't know that one could do this (or that clang-format would try to wrap
expressions like this). it looks like it's already done in a fair number of
other places in the codebase, although i'm not sure that i see it for other
sequences of == expressions joined by &&.

i won't argue against this here if clang-format does something ugly otherwise,
but would you mind filing a request to make clang-format handle this better, per
the instructions at the bottom of
https://chromium.googlesource.com/chromium/src/+/master/docs/clang_format.md, if
that hasn't been done already? initialization lists and argument lists already
use one-per-line in some cases, and it feels like it makes long strings of && or
|| expressions easier to read as well.

[kylechar, 2017/02/02 21:17:18]

On second though, for consistency with existing code I've removed the empty
comments. I filed crbug.com/688111 to see if one statement per line is possible
with clang-format. I think it helps, at least.

+         parent_display_id == other.parent_display_id &&  //
+         position == other.position &&                    //
+         offset == other.offset &&                        //
+         offset_reference == other.offset_reference;      //
+}
+
+bool DisplayPlacement::operator!=(const DisplayPlacement& other) const {
+  return !operator==(other);
+}
+
 DisplayPlacement& DisplayPlacement::Swap() {
   switch (position) {
     case TOP:
@@ -540,19 +552,7 @@ std::unique_ptr<DisplayLayout> DisplayLayout::Copy() const {
 }
 
 bool DisplayLayout::HasSamePlacementList(const DisplayLayout& layout) const {
-  if (placement_list.size() != layout.placement_list.size())
-    return false;
-  for (size_t index = 0; index < placement_list.size(); index++) {
-    const DisplayPlacement& placement1 = placement_list[index];
-    const DisplayPlacement& placement2 = layout.placement_list[index];
-    if (placement1.position != placement2.position ||
-        placement1.offset != placement2.offset ||
-        placement1.display_id != placement2.display_id ||
-        placement1.parent_display_id != placement2.parent_display_id) {
-      return false;
-    }
-  }
-  return true;
+  return placement_list == layout.placement_list;
 }
 
 std::string DisplayLayout::ToString() const {