Work around rust-lang/rust#41297

See in particular
rust-lang/rust#41297 (comment).
This change should be reverted once a fix for that issue lands.

src/lib.rs

@@ -262,6 +262,8 @@ pub struct Form {
 }
 
 impl Client {
+    // inline to work around https://github.com/rust-lang/rust/issues/41297#issuecomment-312197433
+    #[inline]
     fn init(
         mut self,
         params: webdriver::command::NewSessionParameters,
@@ -428,6 +430,7 @@ impl Client {
         )
     }
 
+    #[inline]
     fn dup(&self) -> Self {
         Client(self.0.clone())
     }
@@ -440,6 +443,7 @@ impl Client {
     /// Helper for determining what URL endpoint to use for various requests.
     ///
     /// This mapping is essentially that of https://www.w3.org/TR/webdriver/#list-of-endpoints.
+    #[inline]
     fn endpoint_for(&self, cmd: &Cmd) -> Result<url::Url, url::ParseError> {
         if let WebDriverCommand::NewSession(..) = *cmd {
             return self.0.wdb.join("/session");
@@ -490,6 +494,7 @@ impl Client {
     /// arguments (if any) into the body.
     ///
     /// [the spec]: https://www.w3.org/TR/webdriver/#list-of-endpoints
+    #[inline]
     fn issue_wd_cmd(
         self,
         cmd: WebDriverCommand<webdriver::command::VoidWebDriverExtensionCommand>,
@@ -741,6 +746,7 @@ impl Client {
             .map(|(this, _)| this)
     }
 
+    #[inline]
     fn current_url_(
         &self,
     ) -> impl Future<Item = (Self, url::Url), Error = error::CmdError> + 'static {
@@ -1025,6 +1031,7 @@ impl Client {
 
     // helpers
 
+    #[inline]
     fn by(
         &self,
         locator: webdriver::command::LocatorParameters,
@@ -1039,6 +1046,7 @@ impl Client {
     }
 
     /// Extract the `WebElement` from a `FindElement` or `FindElementElement` command.
+    #[inline]
     fn parse_lookup(&self, res: Json) -> Result<webdriver::common::WebElement, error::CmdError> {
         if !res.is_object() {
             return Err(error::CmdError::NotW3C(res));
@@ -1069,6 +1077,7 @@ impl Client {
         Err(error::CmdError::NotW3C(Json::Object(res)))
     }
 
+    #[inline]
     fn fixup_elements(&self, args: &mut [Json]) {
         if self.0.legacy {
             for arg in args {