Changes needed for MacOS X 10.4 support....

build/common.gypi

 # Copyright (c) 2009 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.
 
 {
   'variables': {
     # .gyp files should set chromium_code to 1 if they build Chromium-specific
     # code, as opposed to external code.  This variable is used to control
     # such things as the set of warnings to enable, and whether warnings are
     # treated as errors.
@@ skipping 34 matching lines @@
     # Override chromium_mac_pch and set it to 0 to suppress the use of
     # precompiled headers on the Mac.  Prefix header injection may still be
     # used, but prefix headers will not be precompiled.  This is useful when
     # using distcc to distribute a build to compile slaves that don't
     # share the same compiler executable as the system driving the compilation,
     # because precompiled headers rely on pointers into a specific compiler
     # executable's image.  Setting this to 0 is needed to use an experimental
     # Linux-Mac cross compiler distcc farm.
     'chromium_mac_pch%': 1,
 
+    # We normally expect MacOS X 10.5 at runtime in the product generated.
+    # Set to 1 to enable MacOS X 10.4 support where possible.
+    # Harmless to set on other platforms, as it has no effect.
+    # This is designed so that products such as O3D can use some Chrome source
+    # without losing 10.4 support.
+    # Look for support_macosx_10_4 later in the file to see where it turns on
+    # compile flags, defines SUPPORT_MACOSX_10_4 in the C preprocessor,
+    # and changes the Xcode deployment target setting.
+    'support_macosx_10_4%': 0,
+
     # 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,
 
     # Overridable specification for potential use of alternative
     # JavaScript engines.
     'javascript_engine%': 'v8',
 
@@ skipping 539 matching lines @@
           'GCC_TREAT_WARNINGS_AS_ERRORS': 'YES',    # -Werror
           'GCC_VERSION': '4.2',
           'GCC_WARN_ABOUT_MISSING_NEWLINE': 'YES',  # -Wnewline-eof
           'MACOSX_DEPLOYMENT_TARGET': '10.5',       # -mmacosx-version-min=10.5
           'PREBINDING': 'NO',                       # No -Wl,-prebind
           'SDKROOT': 'macosx10.5',                  # -isysroot
           'USE_HEADERMAP': 'NO',
           'WARNING_CFLAGS': ['-Wall', '-Wendif-labels'],
           'conditions': [
             ['chromium_mac_pch', {'GCC_PRECOMPILE_PREFIX_HEADER': 'YES'},
-                                 {'GCC_PRECOMPILE_PREFIX_HEADER': 'NO'}],
+                                 {'GCC_PRECOMPILE_PREFIX_HEADER': 'NO'}
+            ],
+            ['support_macosx_10_4',
+              {
+                'OTHER_CFLAGS': ['-D', 'SUPPORT_MACOSX_10_4',],
+                'MACOSX_DEPLOYMENT_TARGET': '10.4',  # mmacosx-version-min=10.4
+              },
+              {
+                'MACOSX_DEPLOYMENT_TARGET': '10.5',  # mmacosx-version-min=10.5
+              }
+            ],
           ],
         },
         'target_conditions': [
           ['_type!="static_library"', {
             'xcode_settings': {'OTHER_LDFLAGS': ['-Wl,-search_paths_first']},
           }],
           ['_mac_bundle', {
             'xcode_settings': {'OTHER_LDFLAGS': ['-Wl,-ObjC']},
           }],
           ['_type=="executable" or _type=="shared_library"', {
@@ skipping 170 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',
   },
 }