Make chrome GN build work in component mode.

content/public/app/BUILD.gn

 # Copyright 2014 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.
 
-# Used internally to hold the sources shared between the various targets below.
-source_set("app_shared_sources") {
-  # content_main_delegate.cc has ifdefs that depend on whether the file is
-  # being used in the context of the browser or child process. So that file has
-  # to be included in the per-type targets below rather than in this shared one.
-  sources = [
-    "android_library_loader_hooks.h",
-    "content_main.h",
-    "content_main_runner.h",
-    "startup_helper_win.h",
-  ]
+# App different than the regular content subcomponents (see comments in
+# //content/BUILD.gn) because it has to support the browser/child process split
+# (the "both" target include both browser and child process files and is used
+# for testing).
+#
+# In non-component mode, browser, child, and both all follow the same structure:
+# foo ->
+#   //content/public/app:child (group) ->
+#     //content/public/app:child_sources (source set) ->
+#       //content/app:child (source set)
 
-  configs += [ "//content:content_implementation" ]
+# In component mode, content is linked as one big turd so there is only one
+# app target containing sources ("both") and the other ones forward to it:
+# foo ->
+#   //content/public/app:child (group; "browser" and "both" ones look the same)
+#     //content (shared library) ->
+#       //content/public/app:both_sources (source set)
 
-  deps = [
-    "//base",
-    "//base:i18n",
-    "//content:export",
-    "//content/common",
-    "//content/public/plugin",
-    "//content/public/renderer",
-    "//content/public/utility",
-  ]
-}
+public_app_shared_sources = [
+  "android_library_loader_hooks.h",
+  "content_main.h",
+  "content_main_delegate.cc",
+  "content_main_delegate.h",
+  "content_main_runner.h",
+  "startup_helper_win.h",
+]
 
-# The structure of this is like the private content/app implementation.
+public_app_shared_deps = [
+  "//base",
+  "//base:i18n",
+  "//content:export",
+  "//content/public/common:common_sources",
+]
+
 if (is_component_build) {
 
-  source_set("app") {
-    sources = [
-      "content_main_delegate.cc",
-      "content_main_delegate.h",
-    ]
+  source_set("both_sources") {
+    # Only the main content shared library can pull this in.
+    visibility = [ "//content:content" ]
 
-    deps = [
-      ":app_shared_sources",
-      "//content/app",
-      "//content/common",
-      "//content/public/browser",
+    sources = public_app_shared_sources
+
+    configs += [ "//content:content_implementation" ]
+
+    deps = public_app_shared_deps + [
+      "//content/app:both",
+      "//content/public/browser:browser_sources",
     ]
   }
+
+  # These all just forward to content, which in turn depends on "both_sources".
   group("browser") {
     deps = [ "//content" ]
   }
   group("child") {
     deps = [ "//content" ]
   }
   group("both") {
     deps = [ "//content" ]
   }
 
 } else {
 
-  source_set("browser") {
-    # See comment in "child" target.
-    check_includes = false
-    sources = [
-      "content_main_delegate.cc",
-      "content_main_delegate.h",
-    ]
-    deps = [
-      ":app_shared_sources",
-      "//content/app:browser",
-      "//content/public/browser",
-      "//content/public/common",
-    ]
-  }
-  source_set("child") {
-    # content_main_delegate.cc conditionally includes content_browser_client.h
-    # from //content/public/browser when it's not the child build. However,
-    # the header checker doesn't know this doesn't apply and throws an error.
-    #
-    # TODO(brettw) either teach the header checker to understand simple
-    # ifdefs or split the file apart so we can enable header checking here.
-    # Furthermore, since this file exists in more than one target, they all
-    # have to opt-out of header checking (a file is checked once for all
-    # targets using a source file).
-    check_includes = false
+  # content_main_delegate.cc conditionally includes content_browser_client.h
+  # from //content/public/browser when it's not the child build. However,
+  # the header checker doesn't know this doesn't apply and throws an error.
+  # So all of these targets set check_includes = false.
+  #
+  # TODO(brettw) either teach the header checker to understand simple
+  # ifdefs or split the file apart so we can enable header checking here.
+  # Furthermore, since this file exists in more than one target, they all
+  # have to opt-out of header checking (a file is checked once for all
+  # targets using a source file).
 
-    sources = [
-      "content_main_delegate.cc",
-      "content_main_delegate.h",
-    ]
-    deps = [
-      ":app_shared_sources",
-      "//content/app:child",
-      "//content/public/common",
-    ]
-  }
   source_set("both") {
-    # See comment in "child" target.
-    check_includes = false
-    sources = [
-      "content_main_delegate.cc",
-      "content_main_delegate.h",
-    ]
-    deps = [
-      ":app_shared_sources",
+    check_includes = false  # See comment above.
+
+    sources = public_app_shared_sources
+    configs += [ "//content:content_implementation" ]
+    deps = public_app_shared_deps + [
       "//content/app:both",
       "//content/public/browser",
       "//content/public/common",
     ]
   }
 
+  # TODO(GYP) enable chrome_multiple_dll support
+  is_chrome_multiple_dll = false
+
+  if (is_chrome_multiple_dll) {
+    source_set("browser") {
+      check_includes = false  # See comment above.
+
+      sources = public_app_shared_sources
+
+      defines = [ "CHROME_MULTIPLE_DLL_BROWSER" ]
+      configs += [ "//content:content_implementation" ]
+
+      deps = public_app_shared_deps + [
+        "//content/app:browser",
+        "//content/public/browser",
+        "//content/public/common",
+      ]
+    }
+
+    source_set("child") {
+      check_includes = false  # See comment above.
+
+      sources = public_app_shared_sources
+
+      defines = [ "CHROME_MULTIPLE_DLL_CHILD" ]
+      configs += [ "//content:content_implementation" ]
+
+      deps = public_app_shared_deps + [
+        "//content/app:child",
+        "//content/public/common",
+      ]
+    }
+  } else {
+    # When the multi-DLL build is disabled, there is only one type of the
+    # "app" target, and "browser" and "child" are the same as "both".
+    group("browser") {
+      deps = [ ":both" ]
+    }
+    group("child") {
+      deps = [ ":both" ]
+    }
+  }
+
 }