If asan==1:

build/common.gypi

Index: build/common.gypi
===================================================================
--- build/common.gypi	(revision 111574)
+++ build/common.gypi	(working copy)
@@ -1923,17 +1923,17 @@
           ['asan==1', {
             # Only in the linux section for now, since ASAN doesn't
             # work on Mac yet.
-	    # TODO(glider): -fasan is deprecated. Remove it when we stop using
-	    # it.
+            # TODO(glider): -fasan is deprecated. Remove it when we stop using
+            # it.
             'cflags': [
               '-fasan',
-	      '-faddress-sanitizer',
+              '-faddress-sanitizer',
               '-w',
-	      '-DADDRESS_SANITIZER',
+              '-DADDRESS_SANITIZER',
             ],
             'ldflags': [
               '-fasan',
-	      '-faddress-sanitizer',
+              '-faddress-sanitizer',
             ],
           }],
           ['no_strict_aliasing==1', {
@@ -2327,8 +2327,33 @@
                  'asan_saves_file': 'asan.saves',
                 },
                 'xcode_settings': {
-                  'CHROMIUM_STRIP_SAVE_FILE': '<(asan_saves_file)'
+                  'CHROMIUM_STRIP_SAVE_FILE': '<(asan_saves_file)',
+                  'OTHER_CFLAGS': [
+                    '-fasan',
+                    '-faddress-sanitizer',
+                    '-w',
+                  ],
+                  'OTHER_LDFLAGS': [
+                    '-fasan',
+                    '-faddress-sanitizer',
+                    # The symbols below are referenced in the ASan runtime
+                    # library (compiled on OS X 10.6), but may be unavailable 
+                    # on the prior OS X versions. Because Chromium is currently
+                    # targeting 10.5.0, we need to explicitly mark these
+                    # symbols as dynamic_lookup.
+                    '-Wl,-U,_malloc_default_purgeable_zone',
+                    '-Wl,-U,_malloc_zone_memalign',
+                    '-Wl,-U,_dispatch_sync_f',
+                    '-Wl,-U,_dispatch_async_f',
+                    '-Wl,-U,_dispatch_barrier_async_f',
+                    '-Wl,-U,_dispatch_group_async_f',
+                    '-Wl,-U,_dispatch_after_f',
+
+                  ],
                 },
+                'defines': [
+                  'ADDRESS_SANITIZER',
+                ],
               }],
             ],
             'target_conditions': [