Rollup merge of rust-lang#102280 - notriddle:notriddle/band, r=GuillaumeGomez

rustdoc: clean up `.out-of-band`/`.in-band` CSS

|        | method | impl
|--------|--------|------
| before | ![image](https://user-images.githubusercontent.com/1593513/192164603-dea9befb-0f5f-4bd5-a44d-1f8328e27955.png) | ![image](https://user-images.githubusercontent.com/1593513/192164642-06f958cb-8fd5-4b73-bdb7-d2778f358f80.png)
| after  | ![image](https://user-images.githubusercontent.com/1593513/192164612-f72ee8db-c87c-477c-99e8-283b1cf0c14b.png) | ![image](https://user-images.githubusercontent.com/1593513/192164653-8e628dc3-5bf3-4ce8-829b-06e27a90fe06.png)

* Remove the `float: right` fallback from the main header, which hasn't been needed since IE11 support was dropped.

* Remove `in-band` from low-level headers, which hasn't been needed since `.rightside` switched to `float: right` in rust-lang@593d6d1

* Remove unreachable `.in-band > code, .in-band > .code-header` CSS, since the `in-band` class was attached to the `code-header` itself, not nested directly below it.

* Use `rem` instead of `em` for code header margins.

* This results in a slight change in spacing around impls and item-info, but since it makes it more consistent with the way methods are presented, it's probably fine.

Preview: http://notriddle.com/notriddle-rustdoc-demos/band/std/fs/struct.File.html

Author: fee1-dead

src/librustdoc/html/render/mod.rs

@@ -1790,7 +1790,7 @@ pub(crate) fn render_impl_summary(
     write!(w, "<section id=\"{}\" class=\"impl has-srclink\"{}>", id, aliases);
     render_rightside(w, cx, &i.impl_item, containing_item, RenderMode::Normal);
     write!(w, "<a href=\"#{}\" class=\"anchor\"></a>", id);
-    write!(w, "<h3 class=\"code-header in-band\">");
+    write!(w, "<h3 class=\"code-header\">");
 
     if let Some(use_absolute) = use_absolute {
         write!(w, "{}", inner_impl.print(use_absolute, cx));

src/librustdoc/html/static/css/rustdoc.css

@@ -176,8 +176,8 @@ h4.code-header {
 	border-bottom-style: none;
 	margin: 0;
 	padding: 0;
-	margin-top: 0.6em;
-	margin-bottom: 0.4em;
+	margin-top: 0.6rem;
+	margin-bottom: 0.4rem;
 }
 .impl,
 .impl-items .method,
@@ -658,18 +658,17 @@ h2.location a {
 	overflow-x: auto;
 }
 
-.content .out-of-band {
+.out-of-band {
 	flex-grow: 0;
 	font-size: 1.125rem;
 	font-weight: normal;
-	float: right;
 }
 
 .method > .code-header, .trait-impl > .code-header {
 	display: block;
 }
 
-.content .in-band {
+.in-band {
 	flex-grow: 1;
 	margin: 0px;
 	padding: 0px;
@@ -682,10 +681,6 @@ h2.location a {
 	background-color: var(--main-background-color);
 }
 
-.in-band > code, .in-band > .code-header {
-	display: inline-block;
-}
-
 .docblock code, .docblock-short code,
 pre, .rustdoc.source .example-wrap {
 	background-color: var(--code-block-background-color);
@@ -1731,13 +1726,13 @@ in storage.js plus the media query with (min-width: 701px)
 		flex-direction: column;
 	}
 
-	.content .out-of-band {
+	.out-of-band {
 		text-align: left;
 		margin-left: initial;
 		padding: initial;
 	}
 
-	.content .out-of-band .since::before {
+	.out-of-band .since::before {
 		content: "Since ";
 	}
 
@@ -1969,7 +1964,7 @@ in storage.js plus the media query with (min-width: 701px)
 }
 
 @media print {
-	nav.sidebar, nav.sub, .content .out-of-band, a.srclink, #copy-path,
+	nav.sidebar, nav.sub, .out-of-band, a.srclink, #copy-path,
 	details.rustdoc-toggle[open] > summary::before, details.rustdoc-toggle > summary::before,
 	details.rustdoc-toggle.top-doc > summary {
 		display: none;