Enable the multi_dll build of Chrome in GN on Windows

build/config/chrome_build.gni

Index: build/config/chrome_build.gni
diff --git a/build/config/chrome_build.gni b/build/config/chrome_build.gni
index 0a0d4fd09a6cdacb899e7f5f4dae0bea784ca1f0..e2ff123543c61c474888854cb24fc3506f08a7df 100644
--- a/build/config/chrome_build.gni
+++ b/build/config/chrome_build.gni
@@ -18,6 +18,5 @@ declare_args() {
   # Break chrome.dll into multple pieces based on process type. Only available
   # on Windows.
   # TODO(brettw) make this work. When it does, the declaration should be:
-  #is_multi_dll_chrome = is_win && !is_component_build
-  is_multi_dll_chrome = false
+  is_multi_dll_chrome = is_win && !is_component_build
 }