Commits on Dec 2, 2016

1. layout: Replace `ConstructionResult::swap_out()` with …

   `ConstructionResult::get()`.
   
   It only actually swaps out in nonincremental mode (which isn't suitable
   for real world use), so the name is confusing.

   

   pcwalton committed Dec 2, 2016
   2a199a4

2. script: Detect when the page is using `requestAnimationFrame()` for …

   non-animation purposes and back off to a timer if so.
   
   After this patch, when the page calls `requestAnimationFrame()` too many
   times in the row without actually mutating the DOM, further calls to
   `rAF` will actually perform the moral equivalent of `setTimeout(16)`.
   This saves a lot of CPU time compared to actually waiting for the
   vertical blanking interval, because waiting for that requires us to draw
   the page.
   
   Reduces CPU usage drastically on nytimes.com, which has a perpetual
   `requestAnimationFrame()` loop that checks whether ads are in view.

   

   pcwalton committed Dec 2, 2016
   ba274c9

3. query: Stop searching the entire flow tree to resolve script-to-layout …

   queries.
   
   Instead of searching the entire tree to find the applicable fragment, we
   use the flow construction result of the nearest DOM node to find the
   flow we're looking for directly. We then recursively do this with
   ancestor DOM nodes in order to find the entire flow tree path,
   performing breadth first search to deal with anonymous flows in between.
   
   To fully eliminate the search, we will probably want some combination of
   (a) parent pointers in the flow tree and (b) rewritten script-to-layout
   queries that don't depend on visiting all ancestor flows of the query
   node. But this is a quick and dirty solution that dramatically improves
   the performance of layout queries.
   
   This is a large responsiveness increase on nytimes.com.

   

   pcwalton committed Dec 2, 2016
   3624625

4. layout_thread: Don't propagate dirty bits around the tree if no styles …

   changed and no flows were reconstructed.
   
   This saves a tree traversal. It also has the side effect of making
   incremental reflow bugs of the form "a dirty bit is never cleared" less
   likely to ruin the performance of layout queries.

   

   pcwalton committed Dec 2, 2016
   39a7ca2

5. layout_thread: Assert that we removed the `REPAINT` flag from the root …

   after building display lists.

   

   pcwalton committed Dec 2, 2016
   4139fd0

6. layout_thread: Minor style cleanup.

   

   pcwalton committed Dec 2, 2016

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