commit 7eb6d44457143d7fc314b3bb112b3316aceb17d0
author Fredrik Söderquist <fs@opera.com> Thu Jan 24 11:17:24 2019
committer Commit Bot <commit-bot@chromium.org> Thu Jan 24 11:17:24 2019
tree efefdb984eab9549a0f4256749ad1f7429a6246e
parent 143fb793713caf25b14a09fe33695ade6cb2407e

Make SameSizeAsComputedStyle model reality better

Make a separate SameSizeAsComputedStyleBase struct and inherit from that
instead of composing.
Make sure the access specifiers match (so that for instance the reference
counter will place in the correct spot in the layout).

So the layout changes like:

 *** Dumping AST Record Layout
          0 | struct SameSizeAsComputedStyle
-         0 |   class RefCounted<SameSizeAsComputedStyle> (base)
-         0 |     uint32_t ref_count_
-         8 |   struct SameSizeAsComputedStyle::ComputedStyleBase base_
-         8 |     void *[7] data_refs
-        64 |     unsigned int [4] bitfields_
+         0 |   struct SameSizeAsComputedStyleBase (base)
+         0 |     void *[7] data_refs
+        56 |     unsigned int [4] bitfields
+        72 |   class RefCounted<SameSizeAsComputedStyle> (base)
+        72 |     uint32_t ref_count_
         80 |   void *[1] own_ptrs
         88 |   void * data_ref_svg_style
            | [sizeof=96, dsize=96, align=8,

And to exemplify with the change to field from [1], the change to the
SameSize... structs will be:

          0 | struct blink::SameSizeAsComputedStyle
          0 |   struct blink::SameSizeAsComputedStyleBase (base)
          0 |     void *[7] data_refs
-        56 |     unsigned int [4] bitfields
+        56 |     unsigned int [5] bitfields
-        72 |   class RefCounted<SameSizeAsComputedStyle> (base)
-        72 |     uint32_t ref_count_
+        76 |   class RefCounted<SameSizeAsComputedStyle> (base)
+        76 |     uint32_t ref_count_
         80 |   void *[1] own_ptrs
         88 |   void * data_ref_svg_style
            | [sizeof=96, dsize=96, align=8,

rather than:

          0 |     uint32_t ref_count_
          8 |   struct SameSizeAsComputedStyle::ComputedStyleBase base_
          8 |     void *[7] data_refs
-        64 |     unsigned int [4] bitfields_
+        64 |     unsigned int [5] bitfields_
-        80 |   void *[1] own_ptrs
+        88 |   void *[1] own_ptrs
-        88 |   void * data_ref_svg_style
+        96 |   void * data_ref_svg_style
-           | [sizeof=96, dsize=96, align=8,
+           | [sizeof=104, dsize=104, align=8,
-           |  nvsize=96, nvalign=8]
+           |  nvsize=104, nvalign=8]

Note primarily the layout of |ref_count_| from RefCounted<>.

(Layout data courtesy of 'clang++ -fdump-record-layouts', with slight
edits for improved readability.)

[1] https://chromium-review.googlesource.com/c/chromium/src/+/1421188

Change-Id: I5f34a9bcdf86e3ddb8488bb14e531bba694c919b
Reviewed-on: https://chromium-review.googlesource.com/c/1430010
Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Javier Fernandez <jfernandez@igalia.com>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#625602}