sahel@ are you able to look at this?

Same here on macOS Sierra.

[56139:1547:1006/212646.176659:ERROR:web_input_event_builders_mac.mm(555)] Not implemented reached in static blink::WebGestureEvent content::WebGestureEventBuilder::Build(NSEvent *, NSView *)

Build: e7f0416cefe3af6fee4921a25611b0af4cedf868

When logging is enabled, this spams the console log with hundreds of messages. Please investigate and fix this. Raising the priority.

sahel@,
Friendly ping to get an update on this issue as it is marked as stable blocker issue.

Thanks in advance..!

Printing stack trace before https://cs.chromium.org/chromium/src/content/browser/renderer_host/input/web_input_event_builders_mac.mm?type=cs&q=web_input_event_builders_mac.mm&sq=package:chromium&l=555:

0   libbase.dylib                       0x000000010feac83c base::debug::StackTrace::StackTrace(unsigned long) + 28
1   libcontent.dylib                    0x0000000112635aa8 content::WebGestureEventBuilder::Build(NSEvent*, NSView*) + 808
2   libcontent.dylib                    0x00000001126e1e43 -[RenderWidgetHostViewCocoa handleBeginGestureWithEvent:] + 67
3   libcontent.dylib                    0x00000001126e2802 -[RenderWidgetHostViewCocoa scrollWheel:] + 82
4   AppKit                              0x00007fffcfb11d25 -[NSWindow(NSEventRouting) _reallySendEvent:isDelayedEvent:] + 6735
5   AppKit                              0x00007fffcfb0ff0a -[NSWindow(NSEventRouting) sendEvent:] + 541
6   libchrome_dll.dylib                 0x000000010a6bf97f -[ChromeEventProcessingWindow sendEvent:] + 79
7   AppKit                              0x00007fffcf994a92 -[NSApplication(NSEvent) sendEvent:] + 2186
8   libchrome_dll.dylib                 0x00000001091db7da __34-[BrowserCrApplication sendEvent:]_block_invoke + 170
9   libbase.dylib                       0x000000010fed8b2a base::mac::CallWithEHFrame(void () block_pointer) + 10
10  libchrome_dll.dylib                 0x00000001091db5c4 -[BrowserCrApplication sendEvent:] + 260
11  AppKit                              0x00007fffcf20f427 -[NSApplication run] + 1002
12  libbase.dylib                       0x000000010fef7847 base::MessagePumpNSApplication::DoRun(base::MessagePump::Delegate*) + 359
13  libbase.dylib                       0x000000010fef5a5e base::MessagePumpCFRunLoopBase::Run(base::MessagePump::Delegate*) + 110
14  libbase.dylib                       0x000000010fef1b79 base::MessageLoop::Run(bool) + 169
15  libbase.dylib                       0x000000010ff30048 base::RunLoop::Run() + 248
16  libchrome_dll.dylib                 0x00000001091e0c48 ChromeBrowserMainParts::MainMessageLoopRun(int*) + 312
17  libcontent.dylib                    0x00000001122cc664 content::BrowserMainLoop::RunMainMessageLoopParts() + 52
18  libcontent.dylib                    0x00000001122d0386 content::BrowserMainRunnerImpl::Run() + 102
19  libcontent.dylib                    0x00000001122c888c content::BrowserMain(content::MainFunctionParams const&) + 124
20  libcontent.dylib                    0x0000000112dae0e4 content::ContentMainRunnerImpl::Run() + 564
21  libembedder.dylib                   0x000000010fdead82 service_manager::Main(service_manager::MainParams const&) + 2482
22  libcontent.dylib                    0x0000000112dad4b4 content::ContentMain(content::ContentMainParams const&) + 68
23  libchrome_dll.dylib                 0x0000000108c18f2f ChromeMain + 175
24  Chromium                            0x0000000108babde4 main + 404
25  libdyld.dylib                       0x00007fffe6ea9235 start + 1
26  ???                                 0x0000000000000002 0x0 + 2

I think it is related to "Create gesture begin/end events for scroll wheel events" cl reviewed on https://chromium-review.googlesource.com/c/chromium/src/+/616074

erikchen@ could you please take a look? Feel free to reassign it to me if that's not the case.

erikchen@, 
Please check this issue as per C#6 & update the thread accordingly as it is a beta blocker issue.

Thank you..!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f253afd7b5d79b5b738b158302d4f2ce561adf02

commit f253afd7b5d79b5b738b158302d4f2ce561adf02
Author: Erik Chen <erikchen@chromium.org>
Date: Thu Nov 02 19:46:13 2017

Prevent a NOTIMPLEMENTED block from being reached.

When a Cocoa app is built with a 10.11+ SDK, and is run on macOS 10.11+,
gesture{Begin,End} events are no longer sent for scrollWheel: gestures. In order
to reduce the number of logic paths in RenderWidgetHostViewCocoa, we sent the
scrollWheel: begin/end events to gesture{Begin,End} handlers. This means that we
need to update the WebGestureEventBuilder to handle scroll wheel events.

Bug:  768266 
Change-Id: I39b5eea400894687b35aa8ce8dbbbde33a426817
Reviewed-on: https://chromium-review.googlesource.com/751681
Reviewed-by: ccameron <ccameron@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513585}
[modify] https://crrev.com/f253afd7b5d79b5b738b158302d4f2ce561adf02/content/browser/renderer_host/input/web_input_event_builders_mac.mm