Add chrome_split_dll gyp variable, and duplicate chrome_main_dll target

Currently contains chrome_browser_dll target. Removes some paths from browser->webcore
via content that are there due to single process mode, and removes dependency of content
on content_renderer.

Current remaining paths from chrome_browser_dll to webcore: http://i.imgur.com/7WWRvpA.jpg

R=cpu@chromium.org
BUG=237249

Review URL: https://chromiumcodereview.appspot.com/14682014

git-svn-id: http://src.chromium.org/svn/trunk/src/build@198834 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -888,6 +888,10 @@
     # 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
@@ -1809,6 +1813,9 @@
           '<(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.