* Enable generate-link-to-def feature on a rustdoc GUI test

 * Add test for jump-to-def links background color

Author: GuillaumeGomez

Diff for: src/bootstrap/test.rs

@@ -925,6 +925,11 @@ impl Step for RustdocGUI {
                     .env("RUSTDOC", builder.rustdoc(self.compiler))
                     .env("RUSTC", builder.rustc(self.compiler))
                     .current_dir(path);
+                // FIXME: implement a `// compile-flags` command or similar
+                //        instead of hard-coding this test
+                if entry.file_name() == "link_to_definition" {
+                    cargo.env("RUSTDOCFLAGS", "-Zunstable-options --generate-link-to-definition");
+                }
                 builder.run(&mut cargo);
             }
         }

Diff for: src/test/rustdoc-gui/jump-to-def-background.goml

@@ -0,0 +1,23 @@
+// We check the background color on the jump to definition links in the source code page.
+goto: file://|DOC_PATH|/src/link_to_definition/lib.rs.html
+
+// Set the theme to dark.
+local-storage: {"rustdoc-theme": "dark", "rustdoc-preferred-dark-theme": "dark", "rustdoc-use-system-theme": "false"}
+// We reload the page so the local storage settings are being used.
+reload:
+
+assert-css: ("body.source .example-wrap pre.rust a", {"background-color": "rgb(51, 51, 51)"}, ALL)
+
+// Set the theme to ayu.
+local-storage: {"rustdoc-theme": "ayu", "rustdoc-preferred-dark-theme": "ayu", "rustdoc-use-system-theme": "false"}
+// We reload the page so the local storage settings are being used.
+reload:
+
+assert-css: ("body.source .example-wrap pre.rust a", {"background-color": "rgb(51, 51, 51)"}, ALL)
+
+// Set the theme to light.
+local-storage: {"rustdoc-theme": "light", "rustdoc-use-system-theme": "false"}
+// We reload the page so the local storage settings are being used.
+reload:
+
+assert-css: ("body.source .example-wrap pre.rust a", {"background-color": "rgb(238, 238, 238)"}, ALL)

Diff for: src/test/rustdoc-gui/src/link_to_definition/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "link_to_definition"
+version = "0.1.0"

Diff for: src/test/rustdoc-gui/src/link_to_definition/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "link_to_definition"
+version = "0.1.0"
+edition = "2018"
+
+[lib]
+path = "lib.rs"

Diff for: src/test/rustdoc-gui/src/link_to_definition/lib.rs

@@ -0,0 +1,6 @@
+pub struct Bar {
+    pub a: String,
+    pub b: u32,
+}
+
+pub fn foo(_b: &Bar) {}