Rustdoc mobile: put out-of-band on its own line

Before this, the item name and the stability, source link, and "collapse
all docs" would compete for room on a single line, resulting in awkward
wrapping behavior on mobile. This gives a separate line for that
out-of-band information. It also removes the "copy path" icon on mobile
to make a little more room.

Also, switch to flex-wrap: wrap, so anytime there's not enough room for
`source`, it gets bumped to the next line.

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

@@ -148,11 +148,11 @@ h1.fqn {
 }
 .main-heading {
 	display: flex;
+	flex-wrap: wrap;
+	justify-content: space-between;
+	border-bottom: 1px dashed #DDDDDD;
+	padding-bottom: 6px;
 	margin-bottom: 15px;
-
-	/* workaround to keep flex from breaking below 700 px width due to the float: right on the nav
-	   above the h1 */
-	padding-left: 1px;
 }
 .main-heading a:hover {
 	text-decoration: underline;
@@ -623,11 +623,7 @@ nav.sub {
 
 .content .out-of-band {
 	flex-grow: 0;
-	text-align: right;
-	margin-left: auto;
-	margin-right: 0;
 	font-size: 1.15rem;
-	padding: 0 0 0 12px;
 	font-weight: normal;
 	float: right;
 }
@@ -1748,10 +1744,25 @@ details.rustdoc-toggle[open] > summary.hideme::after {
 		padding-top: 0px;
 	}
 
-	.rustdoc {
+	.rustdoc,
+	.main-heading {
 		flex-direction: column;
 	}
 
+	.content .out-of-band {
+		text-align: left;
+		margin-left: initial;
+		padding: initial;
+	}
+
+	.content .out-of-band .since::before {
+		content: "Since ";
+	}
+
+	#copy-path {
+		display: none;
+	}
+
 	/* Hide the logo and item name from the sidebar. Those are displayed
 	   in the mobile-topbar instead. */
 	.sidebar .sidebar-logo,

src/test/rustdoc-gui/mobile.goml

@@ -0,0 +1,17 @@
+// Test various properties of the mobile UI
+goto: file://|DOC_PATH|/staged_api/struct.Foo.html
+size: (400, 600)
+
+// The out-of-band info (source, stable version, collapse) should be below the
+// h1 when the screen gets narrow enough.
+assert-css: (".main-heading", {
+  "display": "flex",
+  "flex-direction": "column"
+})
+
+// Note: We can't use assert-text here because the 'Since' is set by CSS and
+// is therefore not part of the DOM.
+assert-css: (".content .out-of-band .since::before", { "content": "\"Since \"" })
+
+size: (1000, 1000)
+assert-css-false: (".content .out-of-band .since::before", { "content": "\"Since \"" })

src/test/rustdoc-gui/toggle-docs-mobile.goml

@@ -1,12 +1,12 @@
 goto: file://|DOC_PATH|/test_docs/struct.Foo.html
 size: (433, 600)
 assert-attribute: (".top-doc", {"open": ""})
-click: (4, 250) // This is the position of the top doc comment toggle
+click: (4, 270) // This is the position of the top doc comment toggle
 assert-attribute-false: (".top-doc", {"open": ""})
-click: (4, 250)
+click: (4, 270)
 assert-attribute: (".top-doc", {"open": ""})
 // To ensure that the toggle isn't over the text, we check that the toggle isn't clicked.
-click: (3, 250)
+click: (3, 270)
 assert-attribute: (".top-doc", {"open": ""})
 
 // Assert the position of the toggle on the top doc block.
@@ -22,10 +22,10 @@ assert-position: (
 // Now we do the same but with a little bigger width
 size: (600, 600)
 assert-attribute: (".top-doc", {"open": ""})
-click: (4, 250) // New Y position since all search elements are back on one line.
+click: (4, 270) // New Y position since all search elements are back on one line.
 assert-attribute-false: (".top-doc", {"open": ""})
-click: (4, 250)
+click: (4, 270)
 assert-attribute: (".top-doc", {"open": ""})
 // To ensure that the toggle isn't over the text, we check that the toggle isn't clicked.
-click: (3, 250)
+click: (3, 270)
 assert-attribute: (".top-doc", {"open": ""})