Auto merge of #6031 - glennw:reftest-race-conditions, r=larsberg,jdm

The basic idea is it's safe to output an image for reftest by testing:
 - That the compositor doesn't have any animations active.
 - That the compositor is not waiting on any outstanding paint messages to arrive.
 - That the script tasks are "idle" and therefore won't cause reflow.
    - This currently means page loaded, onload fired, reftest-wait not active, first reflow triggered.
    - It could easily be expanded to handle pending timers etc.
 - That the "epoch" that the layout tasks have last laid out after script went idle, is reflected by the compositor in all visible layers for that pipeline.

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ports/cef/window.rs

@@ -22,7 +22,6 @@ use layers::geometry::DevicePixel;
 use layers::platform::surface::NativeGraphicsMetadata;
 use libc::{c_char, c_void};
 use msg::constellation_msg::{Key, KeyModifiers};
-use msg::compositor_msg::{ReadyState, PaintState};
 use std::ptr;
 use std_url::Url;
 use util::cursor::Cursor;
@@ -212,26 +211,6 @@ impl WindowMethods for Window {
         }
     }
 
-    fn set_ready_state(&self, ready_state: ReadyState) {
-        let browser = self.cef_browser.borrow();
-        let browser = match *browser {
-            None => return,
-            Some(ref browser) => browser,
-        };
-        let is_loading = match ready_state {
-            ReadyState::Blank | ReadyState::FinishedLoading => 0,
-            ReadyState::Loading | ReadyState::PerformingLayout => 1,
-        };
-        browser.get_host()
-               .get_client()
-               .get_load_handler()
-               .on_loading_state_change(browser.clone(), is_loading, 1, 1);
-    }
-
-    fn set_paint_state(&self, _: PaintState) {
-        // TODO(pcwalton)
-    }
-
     fn hidpi_factor(&self) -> ScaleFactor<ScreenPx,DevicePixel,f32> {
         let browser = self.cef_browser.borrow();
         match *browser {

ports/glutin/window.rs

@@ -14,7 +14,6 @@ use layers::geometry::DevicePixel;
 use layers::platform::surface::NativeGraphicsMetadata;
 use msg::constellation_msg;
 use msg::constellation_msg::Key;
-use msg::compositor_msg::{PaintState, ReadyState};
 use NestedEventLoopListener;
 use std::rc::Rc;
 use std::sync::mpsc::{channel, Sender};
@@ -64,8 +63,6 @@ pub struct Window {
     event_queue: RefCell<Vec<WindowEvent>>,
 
     mouse_pos: Cell<Point2D<i32>>,
-    ready_state: Cell<ReadyState>,
-    paint_state: Cell<PaintState>,
     key_modifiers: Cell<KeyModifiers>,
 }
 
@@ -93,8 +90,6 @@ impl Window {
             mouse_down_point: Cell::new(Point2D(0, 0)),
 
             mouse_pos: Cell::new(Point2D(0, 0)),
-            ready_state: Cell::new(ReadyState::Blank),
-            paint_state: Cell::new(PaintState::Idle),
             key_modifiers: Cell::new(KeyModifiers::empty()),
         };
 
@@ -476,16 +471,6 @@ impl WindowMethods for Window {
          box receiver as Box<CompositorReceiver>)
     }
 
-    /// Sets the ready state.
-    fn set_ready_state(&self, ready_state: ReadyState) {
-        self.ready_state.set(ready_state);
-    }
-
-    /// Sets the paint state.
-    fn set_paint_state(&self, paint_state: PaintState) {
-        self.paint_state.set(paint_state);
-    }
-
     fn hidpi_factor(&self) -> ScaleFactor<ScreenPx, DevicePixel, f32> {
         ScaleFactor::new(self.window.hidpi_factor())
     }
@@ -670,14 +655,6 @@ impl WindowMethods for Window {
          box receiver as Box<CompositorReceiver>)
     }
 
-    /// Sets the ready state.
-    fn set_ready_state(&self, _: ReadyState) {
-    }
-
-    /// Sets the paint state.
-    fn set_paint_state(&self, _: PaintState) {
-    }
-
     fn hidpi_factor(&self) -> ScaleFactor<ScreenPx, DevicePixel, f32> {
         ScaleFactor::new(1.0)
     }

ports/gonk/src/window.rs

@@ -11,9 +11,7 @@ use geom::size::TypedSize2D;
 use layers::geometry::DevicePixel;
 use layers::platform::surface::NativeGraphicsMetadata;
 use libc::c_int;
-use msg::compositor_msg::{ReadyState, PaintState};
 use msg::constellation_msg::{Key, KeyModifiers};
-use std::cell::Cell;
 use std::sync::mpsc::{channel, Sender, Receiver};
 use std::rc::Rc;
 use std::mem::transmute;
@@ -622,9 +620,6 @@ pub struct Window {
     dpy: EGLDisplay,
     ctx: EGLContext,
     surf: EGLSurface,
-
-    ready_state: Cell<ReadyState>,
-    paint_state: Cell<PaintState>,
 }
 
 impl Window {
@@ -750,9 +745,6 @@ impl Window {
             dpy: dpy,
             ctx: ctx,
             surf: eglwindow,
-
-            ready_state: Cell::new(ReadyState::Blank),
-            paint_state: Cell::new(PaintState::Idle),
         };
 
         Rc::new(window)
@@ -787,16 +779,6 @@ impl WindowMethods for Window {
         let _ = egl::SwapBuffers(self.dpy, self.surf);
     }
 
-    /// Sets the ready state.
-    fn set_ready_state(&self, ready_state: ReadyState) {
-        self.ready_state.set(ready_state);
-    }
-
-    /// Sets the paint state.
-    fn set_paint_state(&self, paint_state: PaintState) {
-        self.paint_state.set(paint_state);
-    }
-
     fn set_page_title(&self, _: Option<String>) {
     }