Re-implement PageState serialization without a Blink API dependency.

content/content_common.gypi

Index: content/content_common.gypi
diff --git a/content/content_common.gypi b/content/content_common.gypi
index 4ec69ab68eb6f51428da7c11b1c93b6b8a91a0e4..f9935f2dd0097b0a47377820450b41a6a43b0ef3 100644
--- a/content/content_common.gypi
+++ b/content/content_common.gypi
@@ -56,8 +56,6 @@
     'public/common/media_stream_request.cc',
     'public/common/media_stream_request.h',
     'public/common/page_state.cc',
-    'public/common/page_state_ios.cc',
-    'public/common/page_state_webkit.cc',
     'public/common/page_state.h',
     'public/common/page_transition_types.cc',
     'public/common/page_transition_types.h',
@@ -276,6 +274,8 @@
     'common/net/url_request_user_data.h',
     'common/p2p_messages.h',
     'common/p2p_sockets.h',
+    'common/page_state_serialization.cc',
+    'common/page_state_serialization.h',
     'common/page_zoom.cc',
     'common/pepper_messages.h',
     'common/pepper_plugin_registry.cc',
@@ -359,6 +359,7 @@
         ['include', '^common/media/media_stream_options\\.cc$'],
         ['include', '^common/net/url_fetcher\\.cc$'],
         ['include', '^common/net/url_request_user_data\\.cc$'],
+        ['include', '^common/page_state_serialization\\.cc$'],
         ['include', '^common/savable_url_schemes\\.cc$'],
         ['include', '^common/url_schemes\\.cc$'],
       ],