Add a profile_traits crate to reduce compile times.

A rebuild after touching components/profile/mem.rs now takes 48 seconds (and
only rebuilds `profile` and `servo`) which is much lower than it used to be.
In comparison, a rebuild after touching components/profile_traits/mem.rs takes
294 seconds and rebuilds many more crates.

This change also removes some unnecessary crate dependencies in `net` and
`net_traits`.

components/profile_traits/time.rs

@@ -0,0 +1,95 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+extern crate "time" as std_time;
+extern crate url;
+
+use self::std_time::precise_time_ns;
+use self::url::Url;
+use std::sync::mpsc::Sender;
+
+#[derive(PartialEq, Clone, PartialOrd, Eq, Ord)]
+pub struct TimerMetadata {
+    pub url:         String,
+    pub iframe:      bool,
+    pub incremental: bool,
+}
+
+#[derive(Clone)]
+pub struct ProfilerChan(pub Sender<ProfilerMsg>);
+
+impl ProfilerChan {
+    pub fn send(&self, msg: ProfilerMsg) {
+        let ProfilerChan(ref c) = *self;
+        c.send(msg).unwrap();
+    }
+}
+
+#[derive(Clone)]
+pub enum ProfilerMsg {
+    /// Normal message used for reporting time
+    Time((ProfilerCategory, Option<TimerMetadata>), f64),
+    /// Message used to force print the profiling metrics
+    Print,
+    /// Tells the profiler to shut down.
+    Exit,
+}
+
+#[repr(u32)]
+#[derive(PartialEq, Clone, PartialOrd, Eq, Ord)]
+pub enum ProfilerCategory {
+    Compositing,
+    LayoutPerform,
+    LayoutStyleRecalc,
+    LayoutRestyleDamagePropagation,
+    LayoutNonIncrementalReset,
+    LayoutSelectorMatch,
+    LayoutTreeBuilder,
+    LayoutDamagePropagate,
+    LayoutGeneratedContent,
+    LayoutMain,
+    LayoutParallelWarmup,
+    LayoutShaping,
+    LayoutDispListBuild,
+    PaintingPerTile,
+    PaintingPrepBuff,
+    Painting,
+    ImageDecoding,
+}
+
+#[derive(Eq, PartialEq)]
+pub enum TimerMetadataFrameType {
+    RootWindow,
+    IFrame,
+}
+
+#[derive(Eq, PartialEq)]
+pub enum TimerMetadataReflowType {
+    Incremental,
+    FirstReflow,
+}
+
+pub type ProfilerMetadata<'a> =
+    Option<(&'a Url, TimerMetadataFrameType, TimerMetadataReflowType)>;
+
+pub fn profile<T, F>(category: ProfilerCategory,
+                     meta: ProfilerMetadata,
+                     profiler_chan: ProfilerChan,
+                     callback: F)
+                  -> T
+    where F: FnOnce() -> T
+{
+    let start_time = precise_time_ns();
+    let val = callback();
+    let end_time = precise_time_ns();
+    let ms = (end_time - start_time) as f64 / 1000000f64;
+    let meta = meta.map(|(url, iframe, reflow_type)|
+        TimerMetadata {
+            url: url.serialize(),
+            iframe: iframe == TimerMetadataFrameType::IFrame,
+            incremental: reflow_type == TimerMetadataReflowType::Incremental,
+        });
+    profiler_chan.send(ProfilerMsg::Time((category, meta), ms));
+    return val;
+}