--- a/testing/mozbase/rust/mozrunner/src/runner.rs
+++ b/testing/mozbase/rust/mozrunner/src/runner.rs
@@ -374,34 +374,36 @@ pub mod platform {
 
     /// Searches the system path for `firefox-bin`, then looks for
     /// `Applications/Firefox.app/Contents/MacOS/firefox-bin` under both `/`
     /// (system root) and the user home directory.
     pub fn firefox_default_path() -> Option<PathBuf> {
         if let Some(path) = find_binary("firefox-bin") {
             return Some(path);
         }
+
         let home = env::home_dir();
         for &(prefix_home, trial_path) in [
             (
                 false,
                 "/Applications/Firefox.app/Contents/MacOS/firefox-bin",
             ),
             (true, "Applications/Firefox.app/Contents/MacOS/firefox-bin"),
         ].iter()
         {
-            let path = match (home.as_ref(), prefix_home) {
+            let path = match (home, prefix_home) {
                 (Some(ref home_dir), true) => home_dir.join(trial_path),
                 (None, true) => continue,
-                (_, false) => PathBuf::from(trial_path),
+                (_, false) => trial_path.to_path_buf(),
             };
             if path.exists() {
                 return Some(path);
             }
         }
+
         None
     }
 
     pub fn arg_prefix_char(c: char) -> bool {
         c == '-'
     }
 }
 
@@ -424,26 +426,26 @@ pub mod platform {
             }
         };
         find_binary("firefox.exe")
     }
 
     fn firefox_registry_path() -> Result<Option<PathBuf>, Error> {
         let hklm = RegKey::predef(HKEY_LOCAL_MACHINE);
         for subtree_key in ["SOFTWARE", "SOFTWARE\\WOW6432Node"].iter() {
-            let subtree = try!(hklm.open_subkey_with_flags(subtree_key, KEY_READ));
+            let subtree = hklm.open_subkey_with_flags(subtree_key, KEY_READ)?;
             let mozilla_org = match subtree.open_subkey_with_flags("mozilla.org\\Mozilla", KEY_READ) {
                 Ok(val) => val,
-                Err(_) => continue
+                Err(_) => continue,
             };
-            let current_version: String = try!(mozilla_org.get_value("CurrentVersion"));
-            let mozilla = try!(subtree.open_subkey_with_flags("Mozilla", KEY_READ));
+            let current_version: String = mozilla_org.get_value("CurrentVersion")?;
+            let mozilla = subtree.open_subkey_with_flags("Mozilla", KEY_READ)?;
             for key_res in mozilla.enum_keys() {
-                let key = try!(key_res);
-                let section_data = try!(mozilla.open_subkey_with_flags(&key, KEY_READ));
+                let key = key_res?;
+                let section_data = mozilla.open_subkey_with_flags(&key, KEY_READ)?;
                 let version: Result<String, _> = section_data.get_value("GeckoVer");
                 if let Ok(ver) = version {
                     if ver == current_version {
                         let mut bin_key = key.to_owned();
                         bin_key.push_str("\\bin");
                         if let Ok(bin_subtree) = mozilla.open_subkey_with_flags(bin_key, KEY_READ) {
                             let path: Result<String, _> = bin_subtree.get_value("PathToExe");
                             if let Ok(path) = path {