replace .len() == 0 with is_empty()

closes #7198

components/canvas/canvas_paint_task.rs

@@ -710,7 +710,7 @@ fn write_image(draw_target: &DrawTarget,
                smoothing_enabled: bool,
                composition_op: CompositionOp,
                global_alpha: f32) {
-    if image_data.len() == 0 {
+    if image_data.is_empty() {
         return
     }
     let image_rect = Rect::new(Point2D::zero(), image_size);

components/compositing/compositor.rs

@@ -1320,7 +1320,7 @@ impl<Window: WindowMethods> IOCompositor<Window> {
         // Return unused tiles first, so that they can be reused by any new BufferRequests.
         self.cache_unused_buffers(unused_buffers);
 
-        if layers_and_requests.len() == 0 {
+        if layers_and_requests.is_empty() {
             return false;
         }
 
@@ -1803,4 +1803,3 @@ pub enum CompositingReason {
     /// The window has been zoomed.
     Zoom,
 }
-

components/gfx/display_list/mod.rs

@@ -586,7 +586,7 @@ impl StackingContext {
 
     pub fn print(&self, mut indentation: String) {
         // We cover the case of an empty string.
-        if indentation.len() == 0 {
+        if indentation.is_empty() {
             indentation = "####".to_owned();
         }
 

components/gfx/font_cache_task.rs

@@ -190,7 +190,7 @@ impl FontCache {
             debug!("FontList: Found font family with name={}", &**family_name);
             let s = self.local_families.get_mut(family_name).unwrap();
 
-            if s.templates.len() == 0 {
+            if s.templates.is_empty() {
                 get_variations_for_family(family_name, |path| {
                     s.add_template(Atom::from_slice(&path), None);
                 });

components/gfx/font_context.rs

@@ -222,7 +222,7 @@ impl FontContext {
 
         // If unable to create any of the specified fonts, create one from the
         // list of last resort fonts for this platform.
-        if fonts.len() == 0 {
+        if fonts.is_empty() {
             let mut cache_hit = false;
             for cached_font_entry in self.fallback_font_cache.iter() {
                 let cached_font = cached_font_entry.font.borrow();

components/layout/construct.rs

@@ -707,7 +707,7 @@ impl<'a> FlowConstructor<'a> {
                                               style: &Arc<ComputedValues>) {
         // Fast path: If there is no text content, return immediately.
         let text_content = node.text_content();
-        if text_content.len() == 0 {
+        if text_content.is_empty() {
             return
         }
 

components/layout/css/matching.rs

@@ -571,8 +571,8 @@ impl<'ln> MatchMethods for LayoutNode<'ln> {
                                              &mut applicable_declarations.after);
 
         *shareable = applicable_declarations.normal_shareable &&
-            applicable_declarations.before.len() == 0 &&
-            applicable_declarations.after.len() == 0
+            applicable_declarations.before.is_empty() &&
+            applicable_declarations.after.is_empty()
     }
 
     unsafe fn share_style_if_possible(&self,

components/layout/flow.rs

@@ -1238,7 +1238,7 @@ impl<'a> ImmutableFlowUtils for &'a (Flow + 'a) {
 
     /// Returns true if this flow has no children.
     fn is_leaf(self) -> bool {
-        base(self).children.len() == 0
+        base(self).children.is_empty()
     }
 
     /// Returns the number of children that this flow possesses.

components/net/image_cache_task.rs

@@ -182,7 +182,7 @@ impl ImageCache {
 
             // Can only exit when all pending loads are complete.
             if let Some(ref exit_sender) = exit_sender {
-                if self.pending_loads.len() == 0 {
+                if self.pending_loads.is_empty() {
                     exit_sender.send(()).unwrap();
                     break;
                 }
@@ -388,4 +388,3 @@ pub fn new_image_cache_task(resource_task: ResourceTask) -> ImageCacheTask {
 
     ImageCacheTask::new(ipc_command_sender)
 }
-

components/net_traits/image/base.rs

@@ -44,7 +44,7 @@ fn byte_swap_and_premultiply(data: &mut [u8]) {
 }
 
 pub fn load_from_memory(buffer: &[u8]) -> Option<Image> {
-    if buffer.len() == 0 {
+    if buffer.is_empty() {
         return None;
     }
 
@@ -120,5 +120,3 @@ fn is_gif(buffer: &[u8]) -> bool {
         _ => false
     }
 }
-
-

components/plugins/lints/inheritance_integrity.rs

@@ -83,7 +83,7 @@ impl LintPass for InheritancePass {
                         cx.sess().span_note(*span, "Bare DOM struct found here");
                     }
                 }
-            } else if dom_spans.len() == 0 {
+            } else if dom_spans.is_empty() {
                 cx.span_lint(INHERITANCE_INTEGRITY, cx.tcx.map.expect_item(id).span,
                              "This DOM struct has no reflector or parent DOM struct");
             }

components/script/cors.rs

@@ -232,7 +232,7 @@ impl CORSRequest {
             _ => return error
         };
         // Substep 4
-        if methods.len() == 0 || preflight.mode == RequestMode::ForcedPreflight {
+        if methods.is_empty() || preflight.mode == RequestMode::ForcedPreflight {
             methods = &methods_substep4;
         }
         // Substep 5

components/script/dom/bindings/str.rs

@@ -50,7 +50,7 @@ impl ByteString {
     /// [RFC 2616](http://tools.ietf.org/html/rfc2616#page-17).
     pub fn is_token(&self) -> bool {
         let ByteString(ref vec) = *self;
-        if vec.len() == 0 {
+        if vec.is_empty() {
             return false; // A token must be at least a single character
         }
         vec.iter().all(|&x| {

components/script/dom/document.rs

@@ -970,7 +970,7 @@ impl<'a> DocumentHelpers<'a> for &'a Document {
     /// https://html.spec.whatwg.org/multipage/#dom-window-cancelanimationframe
     fn cancel_animation_frame(self, ident: i32) {
         self.animation_frame_list.borrow_mut().remove(&ident);
-        if self.animation_frame_list.borrow().len() == 0 {
+        if self.animation_frame_list.borrow().is_empty() {
             let window = self.window.root();
             let window = window.r();
             let ConstellationChan(ref chan) = window.constellation_chan();

components/script/dom/htmlscriptelement.rs

@@ -231,7 +231,7 @@ impl<'a> HTMLScriptElementHelpers for &'a HTMLScriptElement {
         }
         // Step 4.
         let text = self.Text();
-        if text.len() == 0 && !element.has_attribute(&atom!("src")) {
+        if text.is_empty() && !element.has_attribute(&atom!("src")) {
             return NextParserState::Continue;
         }
         // Step 5.

components/script/dom/node.rs

@@ -2135,7 +2135,7 @@ impl<'a> NodeMethods for &'a Node {
             NodeTypeId::DocumentFragment |
             NodeTypeId::Element(..) => {
                 // Step 1-2.
-                let node = if value.len() == 0 {
+                let node = if value.is_empty() {
                     None
                 } else {
                     let document = self.owner_doc();

components/script/dom/xmlhttprequest.rs

@@ -497,7 +497,7 @@ impl<'a> XMLHttpRequestMethods for &'a XMLHttpRequest {
         // Step 7
         self.upload_complete.set(match extracted {
             None => true,
-            Some (ref v) if v.len() == 0 => true,
+            Some (ref v) if v.is_empty() => true,
             _ => false
         });
 

components/util/str.rs

@@ -121,14 +121,14 @@ pub enum LengthOrPercentageOrAuto {
 /// Parses a length per HTML5 § 2.4.4.4. If unparseable, `Auto` is returned.
 pub fn parse_length(mut value: &str) -> LengthOrPercentageOrAuto {
     value = value.trim_left_matches(WHITESPACE);
-    if value.len() == 0 {
+    if value.is_empty() {
         return LengthOrPercentageOrAuto::Auto
     }
     if value.starts_with("+") {
         value = &value[1..]
     }
     value = value.trim_left_matches('0');
-    if value.len() == 0 {
+    if value.is_empty() {
         return LengthOrPercentageOrAuto::Auto
     }
 
@@ -171,7 +171,7 @@ pub fn parse_length(mut value: &str) -> LengthOrPercentageOrAuto {
 /// Parses a legacy color per HTML5 § 2.4.6. If unparseable, `Err` is returned.
 pub fn parse_legacy_color(mut input: &str) -> Result<RGBA,()> {
     // Steps 1 and 2.
-    if input.len() == 0 {
+    if input.is_empty() {
         return Err(())
     }
 
@@ -243,7 +243,7 @@ pub fn parse_legacy_color(mut input: &str) -> Result<RGBA,()> {
     let mut input = new_input;
 
     // Step 11.
-    while input.len() == 0 || (input.len() % 3) != 0 {
+    while input.is_empty() || (input.len() % 3) != 0 {
         input.push(b'0')
     }
 

components/util/vec.rs

@@ -35,7 +35,7 @@ impl<T: Ord + PartialOrd + PartialEq> BinarySearchMethods<T> for [T] {
 
 impl<T> FullBinarySearchMethods<T> for [T] {
     fn binary_search_index_by<K,C:Comparator<K,T>>(&self, key: &K, cmp: C) -> Option<usize> {
-        if self.len() == 0 {
+        if self.is_empty() {
             return None;
         }
 

ports/cef/string_multimap.rs

@@ -118,7 +118,7 @@ pub extern "C" fn cef_string_multimap_value(smm: *mut cef_string_multimap_t, ind
 pub extern "C" fn cef_string_multimap_clear(smm: *mut cef_string_multimap_t) {
     unsafe {
         if smm.is_null() { return; }
-        if (*smm).len() == 0 { return; }
+        if (*smm).is_empty() { return; }
         for (_, val) in (*smm).iter_mut() {
             while let Some(cs) = (*val).pop() {
                 cef_string_userfree_utf16_free(cs);