I attempted to get this working locally and here were the steps I had to figure out and follow:

1. Patch common.gypi to suppress errors about invoking unused libraries:

diff --git a/build/common.gypi b/build/common.gypi
index a3b5053..b28bb01 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -2672,6 +2672,7 @@
 
         # TODO(thakis): Enable this,  crbug.com/507717 
         '-Wno-shift-negative-value',
+        '-Wno-error=unused-command-line-argument',
       ],
     },
     'includes': [ 'set_clang_warning_flags.gypi', ],

2. Add distcc to the first two lines of out/Release/build.ninja like this:

 cc = distcc ../../third_party/llvm-build/Release+Asserts/bin/clang
 cxx = distcc ../../third_party/llvm-build/Release+Asserts/bin/clang++

3. Suppress the 'find-bad-constructs' stuff as it passes the path to LibFindBadConstruct.so as an absolute path to participating distcc hosts. If the distcc host doesn't have chromium in the same directory as the primary host, it fails to compile when it is unable to resolve the path:

GYP_DEFINES="asan=1 component=shared_library dcheck_always_on=1 clang_use_chrome_plugins=0" gclient runhooks

There must be a better way or maybe distcc isn't supported?