Add chrome_split_dll gyp variable, and duplicate chrome_main_dll target (reland)

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 870 matching lines @@
     # but that doesn't work as we'd like.
     'msvs_debug_link_incremental%': '2',
 
     # Needed for some of the largest modules.
     'msvs_debug_link_nonincremental%': '1',
 
     # Turns on Use Library Dependency Inputs for linking chrome.dll on Windows
     # to get incremental linking to be faster in debug builds.
     'incremental_chrome_dll%': '0',
 
+    # Experimental setting to break chrome.dll in to chrome_browser.dll and
+    # chrome_child.dll.
+    'chrome_split_dll%': '0',
+
     # The default settings for third party code for treating
     # warnings-as-errors. Ideally, this would not be required, however there
     # is some third party code that takes a long time to fix/roll. So, this
     # flag allows us to have warnings as errors in general to prevent
     # regressions in most modules, while working on the bits that are
     # remaining.
     'win_third_party_warn_as_error%': 'true',
 
     # This is the location of the sandbox binary. Chrome looks for this before
     # running the zygote process. If found, and SUID, it will be used to
@@ skipping 901 matching lines @@
         'cflags_cc+': [
           '-frtti',
           '-gline-tables-only',
           '-fintercept-allocation-functions',
         ],
         'defines': ['TYPE_PROFILING'],
         'dependencies': [
           '<(DEPTH)/base/allocator/allocator.gyp:type_profiler',
         ],
       }],
+      ['chrome_split_dll', {
+        'defines': ['CHROME_SPLIT_DLL'],
+      }],
       ['OS=="linux" and clang==1 and host_arch=="ia32"', {
         # TODO(dmikurube): Remove -Wno-sentinel when Clang/LLVM is fixed.
         # See http://crbug.com/162818.
         'cflags+': ['-Wno-sentinel'],
       }],
       ['OS=="win" and "<(msbuild_toolset)"!=""', {
         'msbuild_toolset': '<(msbuild_toolset)',
       }],
       ['branding=="Chrome"', {
         'defines': ['GOOGLE_CHROME_BUILD'],
@@ skipping 2614 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',
   },
 }