Add test to check width of item-info

Author: GuillaumeGomez

src/test/rustdoc-gui/item-info-width.goml

@@ -0,0 +1,7 @@
+// This test ensures that the item information don't take 100% of the width if unnecessary.
+goto: file://|DOC_PATH|/lib2/struct.Foo.html
+// We set a fixed size so there is no chance of "random" resize.
+size: (1100, 800)
+// We check that ".item-info" is bigger than its content.
+assert-css: (".item-info", {"width": "807px"})
+assert-css: (".item-info .stab", {"width": "343px"})

src/test/rustdoc-gui/src/lib2/lib.rs

@@ -1,5 +1,7 @@
 // ignore-tidy-linelength
 
+#![feature(doc_cfg)]
+
 pub mod module {
     pub mod sub_module {
         pub mod sub_sub_module {
@@ -14,6 +16,7 @@ pub fn foobar() {}
 
 pub type Alias = u32;
 
+#[doc(cfg(feature = "foo-method"))]
 pub struct Foo {
     pub x: Alias,
 }