Update Chromium docs on using clang

docs/clang.md

Index: docs/clang.md
diff --git a/docs/clang.md b/docs/clang.md
index 5b5b43f7ada6624b746e7b4b8a1fc7d747ebe57d..7b43eaf644838846d84ac55652d1164d84f80a01 100644
--- a/docs/clang.md
+++ b/docs/clang.md
@@ -14,12 +14,16 @@ See
 
 ## Build instructions
 
-Get clang (happens automatically during `gclient runhooks` on Mac and Linux):
+### Ninja

[Nico, 2016/04/13 00:50:14]

(we can probably drop this heading too; all platforms are on ninja by now)

+
+Regenerate the ninja build files with Clang enabled. On Linux or Mac, Clang is
+enabled by default.
+
+If you use gyp: `GYP_DEFINES=clang=1 build/gyp_chromium`
 
-    tools/clang/scripts/update.py
+If you use gn, run `gn args` and add `is_clang = true` to your args.gn file.
 
-(Only needs to be run once per checkout, and clang will be automatically updated
-by `gclient runhooks`.)
+Build: `ninja -C out/Debug chrome`
 
 ### Reverting to gcc on linux
 
@@ -29,16 +33,6 @@ don't want to build with clang:
 
     GYP_DEFINES=clang=0 build/gyp_chromium
 
-### Ninja
-
-Regenerate the build files (`clang=1` is on by default on Mac and Linux):
-
-If you use gyp: `GYP_DEFINES=clang=1 build/gyp_chromium`
-
-If you use gn, run `gn args` and add `is_clang = true` to your args.gn file.
-
-Build: `ninja -C out/Debug chrome`
-
 ## Mailing List
 
 http://groups.google.com/a/chromium.org/group/clang/topics
@@ -79,8 +73,6 @@ See [clang_static_analyzer.md](clang_static_analyzer.md).
 
 ## Windows
 
-**Experimental!**
-
 clang can be used as compiler on Windows. Clang uses Visual Studio's linker and
 SDK, so you still need to have Visual Studio installed.
 
@@ -99,7 +91,6 @@ ninja -C out\Debug chrome
 

[Nico, 2016/04/13 00:50:14]

mention somewhere here that update.py only needs to be run once and autoupdates
after that. maybe just paste the "(Only needs to be run once per checkout, and
clang will be …" bit here

[Reid Kleckner, 2016/04/13 18:11:47]

What about simplifying this to `gclient runhooks` here and above? Is that too
slow?

[Nico, 2016/04/13 18:13:58]

It's not enough in a gn build, since runhooks calls update.py with --if-needed,
and that exits on Windows unless clang=1 is in GYP_DEFINES (which it isn't in gn
builds) 

 Current brokenness:
 
-*   Goma doesn't work.
 *   Debug info is very limited.
 *   To get colored diagnostics, you need to be running
     [ansicon](https://github.com/adoxa/ansicon/releases).
@@ -131,3 +122,16 @@ If your clang revision is very different from the one currently used in chromium
 *   Check `tools/clang/scripts/update.py` to find chromium's clang revision
 *   You might have to tweak warning flags. Or you could set `werror=` in the
     line above to disable warnings as errors (but this only works on Linux).
+
+## Using LLD
+
+**Experimental!**
+
+LLD is a relatively new linker from LLVM. The current focus is on Windows and
+Linux support, where it can link Chrome approximately twice as fast as gold and
+MSVC's link.exe as of this writing. LLD does not yet support generating PDB
+files, which makes it hard to debug Chrome while using LLD.
+
+If you use gyp, you can enable it with `GYP_DEFINES=lld=1`. If you use gn, set
+`use_lld = true` in args.gn. Currently this configuration is only supported on
+Windows.