What steps will reproduce the problem?
1. Follow steps to install prerequisites here [1].
2. Follow "Setting up Windows", "Install depot_tools", "Get the code", "Setting up the build" from [2].
3. Attempt "Build Chromium" from [2].

[1] https://webrtc.org/native-code/development/prerequisite-sw/
[2] https://chromium.googlesource.com/chromium/src/+/master/docs/windows_build_instructions.md

What is the expected result?
It builds.

What do you see instead?
λ ninja -C .\out\Default                                                                                                                                  
ninja: Entering directory `.\out\Default'                                                                                                                 
[25/48039] CXX obj/base/base/windows_version.obj                                                                                                          
FAILED: obj/base/base/windows_version.obj                                                                                                                 
ninja -t msvc -e environment.x64 -- "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\BIN\amd64/cl.exe" /nologo /showIncludes /FC @obj/base/base/win
dows_version.obj.rsp /c ../../base/win/windows_version.cc /Foobj/base/base/windows_version.obj /Fd"obj/base/base_cc.pdb"                                  
c:\users\scott\src\gitroot\chromium\src\base\win\windows_version.cc(18): fatal error C1189: #error:  VS 2015 Update 3 with Cumulative Servicing Release or
 higher is required                                                                                                                                       
[34/48039] CXX obj/base/base/trace_log.obj                                                                                                                
ninja: build stopped: subcommand failed.                                                                                                                  

What version of the product are you using? On what operating system?
I'm not sure what "product" you are referring to?
λ git log -1
commit 2efffa89a050e8d0c3c6829f7bd63eb3970f0eaa

I have Microsoft Visual Studio Community 2015 Version 14.0.25421.03 Update 3.

Please provide any additional information below.

Microsoft Visual Studio Community 2015
Version 14.0.25421.03 Update 3
Microsoft .NET Framework
Version 4.6.01586

Installed Version: Community

Visual Basic 2015   00322-20000-00000-AA858
Microsoft Visual Basic 2015

Visual C# 2015   00322-20000-00000-AA858
Microsoft Visual C# 2015

Visual C++ 2015   00322-20000-00000-AA858
Microsoft Visual C++ 2015

Application Insights Tools for Visual Studio Package   7.18.00214.2
Application Insights Tools for Visual Studio

Common Azure Tools   1.8
Provides common services for use by Azure Mobile Services and Microsoft Azure Tools.

End of the Line   1.5
Shows end of line markers in text editor allowing users to differentiate between CRLF and LF line endings.

JavaScript Language Service   2.0
JavaScript Language Service

JavaScript Project System   2.0
JavaScript Project System

JetBrains ReSharper Ultimate 2016.1.2    Build 105.0.20160522.80219
JetBrains ReSharper Ultimate package for Microsoft Visual Studio. For more information about ReSharper Ultimate, visit http://www.jetbrains.com/resharper. Copyright © 2017 JetBrains, Inc.

Microsoft Azure Mobile Services Tools   1.4
Microsoft Azure Mobile Services Tools

NuGet Package Manager   3.4.4
NuGet Package Manager in Visual Studio. For more information about NuGet, visit http://docs.nuget.org/.

PreEmptive Analytics Visualizer   1.2
Microsoft Visual Studio extension to visualize aggregated summaries from the PreEmptive Analytics product.

TypeScript   1.8.34.0
TypeScript tools for Visual Studio

Visual Studio Tools for Unity   2.3.0.0
Visual Studio Tools for Unity

Visual Studio Tools for Universal Windows Apps   14.0.25527.01
The Visual Studio Tools for Universal Windows apps allow you to build a single universal app experience that can reach every device running Windows 10: phone, tablet, PC, and more. It includes the Microsoft Windows 10 Software Development Kit.