Chrome Version: 57.02987.133 (64-bit)
OS: Windows 10

What steps will reproduce the problem?

So these are the top 10 items on Chrome Windows that I’ve encountered on 3 machines.  I’ll try to log this a crbug, but the bugs are pretty numerous in this case.  Our Mac build can detect and isolate the pinch-zoom gesture, but Windows has to treat ctrl+wheel and pinch-zoom the same, despite vastly different deltaY values across machines.  Firefox and Edge have their own issues, but I’ll leave those off.   

Chrome
  I would chalk these up to Windows drivers, but I've seen this behavior across
    three machines.  These behaviors apply to Chrome Windows.
      
  on Dell XPS15 with high-precision touchpad
  on Samsung Notebook Pro 9 with high-precision touchpad
  on Razer Stealth without high-precision touchpad
  
1. applies dpr on Windows to wheel data, but no other browser does.  
    Chrome doesn’t apply dpr on Mac either.

2. all Windows browsers apply numLinesToScroll, but no way to remove this
    there are many scrolling/panning/pinch-zoom cases which should not scale to this
    so need a way to remove it.

3. sends 0.8333, 1.6666, ... repeating deltaX sequences on low speed left-to-right movement
  for wheel deltaXY, but only 0.8333 for slow speed vertically 
  this results in diagonal movements feeling 2x slower vertically
  
4. Mac Chrome and Safari match on values, but pinch-zoom is on completely different
   scale than ctrl+wheel.  Have to convert differently.
   
5. Chrome Windows has no distinguishing feature on key-down event sent on Windows for pinch-zoom vs. actual ctrl+wheel.
  (None of the browsers do).  On Mac, the repeat value is set on the faked event.  Due to 4, this is a big problem.

6. Pinch zoom on Chrome Windows is (on XPS15)
    This means treating both as zoom is difficult, since the values aren't normalized)
    
    // Dell
    //         wdy (divided by dpr)
    // pan     =   1
    // pan-w   =   1
    // zoom    =   1   for ctrl+wheel with touchpad
    // zoom-w  = 120   for ctrl+wheel with Wheel Mouse Optical
    // pinch   = 120   for pinch-zoom with touchpad
    
    // Samsung
    // pan    =   1
    // pan-w  =   1
    // zoom   =   1  
    // zoom-w =   1  <- difference
    // pinch  = 120
    
    // Razer
    // pan    =   1
    // pan-w  =   1
    // zoom   =   4 <- difference
    // zoom-w =   4 <- difference
    // pinch  = 120

7. Mouse movement opposite to existing direction does not send wheel events
  until you exceed a touchpad distance threshold, causing diagonal panning to fail.
  Mouse is locked into horizontal or vertical pan. +/-30 pixel threshold.
  This makes diagonal panning feel really broken.
  
8. I never see a diagonal wheel value (both dx/dy set) on Windows, but do on Mac.  
    Chrome is always sending purely vertical then horizontal events for diagonal movement.
  
9. Seeing spikes in wdy/dy values with inertia.
    Also there are large values at end of inertia that cause abrupt stop.
    This is especially bad on zoom, where we get sudden zoom and the user gets lost.
    Mac has some variation in the delta (not a true ramp up/down, but it’s much better than Windows)

   Pan in a single direction and these are deltaY values that I see on XPS 15.   
    91, 24, 27, 41, 37,45,41,51,46,48,23*,81*,91,69,48,36, 101*, 6*, 45,64,23, 31, 26,25, 17,12, 15, 6 

10. Impossible to identify inertia events in the browser to lock out 
    zoom from pan inertia, or pan from zoom inertia.  So have to look at timestamps.
    The spikes from 3 and 9 mean you can't identify decelerating inertia from delta.

11. Support high-precision touchpad on Windows.  
   Maybe this would provide something other that 120 for pinch.

What is the expected result?

Mac-like touchpad support especially on high-precision touchpads.
Some way to distinguish pinch-zoom
Ability to remove numLinesToScroll.

What happens instead?

There are so many issue above, that it's near impossible to support a canvas that has to zoom, pan, and pinch-zoom without moving to pointer events.  Native OSX apps (and Safari) simply respond to gesture for pinch-zoom, and wheel for zoom/pan.  Often times zoom has an invert preference that should not apply to pinch-zoom.  We currently have to treat zoom and pinch the same on Windows, so the preference applies to both.

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