docs: convert windows build instructions from html to markdown

docs/windows_build_instructions.md

+# Windows Build Instructions
+
+## Setting up Windows
+
+You must set your Windows system locale to English, or else you may get
+build errors about "The file contains a character that cannot be
+represented in the current code page."
+
+### Setting up the environment for Visual Studio
+
+You must build with Visual Studio 2013 Update 4 or Visual Studio 2015
+Update 1, no other versions are supported.
+
+You must have Windows 7 x64 or later. x86 OSs are unsupported.
+
+1.  Get
+[depot\_tools](http://commondatastorage.googleapis.com/chrome-infra-docs/flat/depot_tools/docs/html/depot_tools_tutorial.html#_setting_up).
+2.  Follow the appropriate path below:
+
+### Open source contributors
+
+For building with Visual Studio 2013 (no longer default as of March 10,
+2016, and not recommended - requires setting GYP\_MSVS\_VERSION=2013):
+
+> Install [Visual Studio 2013
+> Community](http://www.visualstudio.com/products/visual-studio-community-vs)
+> or [Visual Studio 2013
+> Professional](http://www.visualstudio.com/products/visual-studio-professional-with-msdn-vs)
+> depending on which license is appropriate for you. You can deselect
+> the default options if you want, but you must make sure to install
+> "Microsoft Foundation Classes for C++".
+> \
+> You should also install the [Windows 10
+> SDK](https://dev.windows.com/en-us/downloads/windows-10-sdk) to the
+> default install location. You must have SDK version 10.0.10586 or
+> greater installed.
+
+For building with Visual Studio 2015 (default compiler as of March 10,
+2016):

[Dirk Pranke, 2016/03/22 18:36:17]

I would probably put these instructions before the 2013 instructions now.

[tfarina, 2016/03/23 12:16:48]

Done.

+
+> Install Visual Studio 2015 Update 1 or later - Community Edition
+> should work if its license is appropriate for you. Be sure to select
+> Custom install and select VC++ (which selects three sub-categories
+> including MFC) and, under Universal Windows App Development Tools,
+> select Tools (1.2) and Windows 10 SDK (10.0.10586). You must have the
+> 10586 SDK installed or else you will hit compile errors such as
+> redefined macros.
+
+Run `set DEPOT\_TOOLS\_WIN\_TOOLCHAIN=0`, or set that variable in your
+global environment.
+
+Visual Studio Express 2013 is **not** supported and will not be able to
+build Chromium.
+
+Compilation is done through ninja, **not** Visual Studio.
+
+### Google employees
+
+Run: `download\_from\_google\_storage --config` and follow the
+authentication instructions.**Note that you must authenticate with your
+@google.com credentials**, not @chromium.org. Enter "0" if asked for a
+project-id.
+
+Once you've done this, the toolchain will be installed automatically for
+you in Step 3, below (near the end of the step).
+
+The toolchain will be in depot\_tools\\win\_toolchain, and windbg can be
+found in
+depot\_tools\\win\_toolchain\\vs2013\_files\\win8sdk\\Debuggers.
+
+If you want the IDE for debugging and editing, you will need to install
+it separately, but this is optional and not needed to build Chromium.
+
+## Getting the Code
+
+Follow the steps to [check out the
+code](https://www.chromium.org/developers/how-tos/get-the-code) (largely
+"fetch chromium").
+
+## Building
+
+Build the target you are interested in.
+
+```shell
+ninja -C out\\Debug chrome
+```
+
+Alternative (Graphical user interface): Open a generated .sln
+file such as all.sln, right-click the chrome project and select build.
+This will invoke the real step 4 above. Do not build the whole solution
+since that conflicts with ninja's build management and everything will
+explode.
+Substitute the build directory given to -C with out\\Debug\_x64 for
+[64-bit
+builds](https://www.chromium.org/developers/design-documents/64-bit-support)
+in GYP, or whatever build directory you have configured if using GN.
+
+### Performance tips
+
+1.  Have many and fast CPU cores and enough RAM to keep them all busy.
+    (Minimum recommended is 4-8 fast cores and 16-32 GB of RAM)
+2.  Reduce file system overhead by excluding build directories from
+    antivirus and indexing software.
+3.  Store the build tree on a fast disk (preferably SSD).
+4.  If you are primarily going to be doing debug development builds, you
+    use the component build (in
+    [GYP](https://www.chromium.org/developers/gyp-environment-variables)
+    do set GYP\_DEFINES=component=shared\_library, in
+    [GN](https://www.chromium.org/developers/gn-build-configuration),
+    set the build arg is\_component\_build = true). This will generate
+    many DLLs and enable incremental linking, which makes linking
+    *much*faster in Debug.
+
+Still expect build times of 30 minutes to 2 hours when everything has to
+be recompiled.