Split //ios/chrome/browser in multiple targets.

ios/chrome/browser/share_extension/BUILD.gn

Index: ios/chrome/browser/share_extension/BUILD.gn
diff --git a/ios/chrome/browser/share_extension/BUILD.gn b/ios/chrome/browser/share_extension/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..f8cc09a4b0d758813d1bc11c12ac2cec63556d99
--- /dev/null
+++ b/ios/chrome/browser/share_extension/BUILD.gn
@@ -0,0 +1,28 @@
+# Copyright 2016 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.
+
+source_set("share_extension") {
+  sources = [
+    "share_extension_item_receiver.h",
+    "share_extension_item_receiver.mm",
+    "share_extension_service.h",
+    "share_extension_service.mm",
+    "share_extension_service_factory.cc",
+    "share_extension_service_factory.h",
+  ]
+  deps = [
+    "//base",
+    "//components/bookmarks/browser",
+    "//components/keyed_service/core",
+    "//components/keyed_service/ios",
+    "//ios/chrome/browser:browser_no_public_deps",
+    "//ios/chrome/browser/bookmarks",
+    "//ios/chrome/browser/browser_state",
+    "//ios/chrome/browser/reading_list",
+    "//ios/chrome/common/app_group",
+    "//ios/web",
+    "//net",
+    "//url",
+  ]
+}