Roll mac toolchain to include 10.11.

This is the same as the previous toolchain (Xcode 5.1.1 with 10.10 SDK), but
also includes the 10.11 SDK.

BUG=474373, 626093

Review-Url: https://codereview.chromium.org/2323523003
Cr-Commit-Position: refs/heads/master@{#417392}

build/mac_toolchain.py

@@ -30,7 +30,7 @@ import urllib2
 
 # This can be changed after running /build/package_mac_toolchain.py.
 TOOLCHAIN_REVISION = '5B1008'
-TOOLCHAIN_SUB_REVISION = 2
+TOOLCHAIN_SUB_REVISION = 3
 TOOLCHAIN_VERSION = '%s-%s' % (TOOLCHAIN_REVISION, TOOLCHAIN_SUB_REVISION)
 
 BASE_DIR = os.path.abspath(os.path.dirname(__file__))