Add a postbuild action for executables built with ASan on Mac OS.

build/common.gypi

Index: build/common.gypi
===================================================================
--- build/common.gypi	(revision 187295)
+++ build/common.gypi	(working copy)
@@ -1658,6 +1658,11 @@
     # throughout the codebase.
     'defines' : ['USE_SKIA'],
     'conditions': [
+      ['asan==1', {
+        'dependencies': [
+          '<(DEPTH)/build/mac/asan.gyp:asan_dynamic_runtime',
+        ],
+      }],
       ['OS=="linux" and linux_use_tcmalloc==1 and clang_type_profiler==1', {
         'cflags_cc!': ['-fno-rtti'],
         'cflags_cc+': [
@@ -3530,6 +3535,29 @@
           }],
           ['_mac_bundle', {
             'xcode_settings': {'OTHER_LDFLAGS': ['-Wl,-ObjC']},
+            'target_conditions': [
+              ['_type=="executable"', {
+                'conditions': [
+                  ['asan==1', {
+                    'postbuilds': [
+                      {
+                        'variables': {
+                          # Define copy_asan_dylib_path in a variable ending in
+                          # _path so that gyp understands it's a path and
+                          # performs proper relativization during dict merging.
+                          'copy_asan_dylib_path':
+                            'mac/copy_asan_runtime_dylib.sh',
+                        },
+                        'postbuild_name': 'Copy ASan runtime dylib',
+                        'action': [
+                          '<(copy_asan_dylib_path)',
+                        ],
+                      },
+                    ],
+                  }],
+                ],
+              }],
+            ],
           }],
         ],  # target_conditions
       },  # target_defaults