Change the Mac OS X Deployment Target from 10.5 to 10.6.

build/common.gypi

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 623 matching lines @@
     # and corresponds to the MAC_OS_X_VERSION_MAX_ALLOWED compile-time macro.
     # "Maximum allowed" refers to the operating system version whose APIs are
     # available in the headers.
     # The deployment target identifies the minimum system version that the
     # built products are expected to function on.  It corresponds to the
     # MAC_OS_X_VERSION_MIN_REQUIRED compile-time macro.
     # To ensure these macros are available, #include <AvailabilityMacros.h>.
     # Additional documentation on these macros is available at
     # http://developer.apple.com/mac/library/technotes/tn2002/tn2064.html#SECTION3
     # Chrome normally builds with the Mac OS X 10.6 SDK and sets the
-    # deployment target to 10.5.  Other projects, such as O3D, may override
+    # deployment target to 10.6.  Other projects, such as O3D, may override
     # these defaults. If the SDK is installed someplace that Xcode doesn't
     # know about, set mac_sdk_path to the path to the SDK. If set to a
     # non-empty string, mac_sdk_path will be used in preference to mac_sdk.
     # mac_sdk gets its default value elsewhere in this file.
     'mac_sdk_path%': '',
-    'mac_deployment_target%': '10.5',
+    'mac_deployment_target%': '10.6',
 
     # The default value for mac_strip in target_defaults. This cannot be
     # set there, per the comment about variable% in a target_defaults.
     'mac_strip_release%': 1,
 
     # Set to 1 to enable code coverage.  In addition to build changes
     # (e.g. extra CFLAGS), also creates a new target in the src/chrome
     # project file called "coverage".
     # Currently ignored on Windows.
     'coverage%': 0,
@@ skipping 2672 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }