Add experimental support for compiling with clang and ASan on Linux.

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index 85f5090ec4a5ddeabc123fff78cbb7c59da5ba43..5e87ec9176deb415dc8b0f610ce78c7604b2d4a9 100644
--- a/DEPS
+++ b/DEPS
@@ -16,6 +16,9 @@ deps = {
   "testing/gtest":
      "https://chromium.googlesource.com/external/googletest.git@8245545b6dc9c4703e6496d1efd19e975ad2b038",
 
+  "tools/clang":
+    "https://chromium.googlesource.com/chromium/src/tools/clang",
+
   "v8":
     "https://chromium.googlesource.com/v8/v8.git@9081ee11af0311aecb152bfe80330fc1bf6085e6",
 
@@ -78,4 +81,11 @@ hooks = [
                 '-s', 'buildtools/linux64/clang-format.sha1',
     ],
   },
+  {
+    # Pull clang if needed or requested via GYP_DEFINES.
+    # Note: On Win, this should run after win_toolchain, as it may use it.

[Nico, 2015/10/15 23:41:22]

There's no win_toolchain step here, so you probably want to remove this comment
(and check that runhooks continues to work on windows)

[Oliver Chang, 2015/10/16 00:52:15]

Done.

+    'name': 'clang',
+    'pattern': '.',
+    'action': ['python', 'tools/clang/scripts/update.py', '--if-needed'],
+  },
 ]