Move content::WebPreferences struct to Blink

As the first step to convert ViewMsg_UpdateWebPreferences,
we need to move WebPreferences from //content to
//third_party/blink because the IPC message passes WebPreferences
struct.

So, this CL moves WebPreferences to
//third_party/blink/public/common/web_preferences as
a pre-work.

Additionally, this CL wraps all enums and WebPreferences
with web_pref namespace to avoid duplicating the existing
enum types in bliink.

AX-Relnotes: N/A

Bug: 1097943
Change-Id: I35b3dbd45a8bc4bc36a55d7f185d3247fd0b1714
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2397670
Commit-Queue: Gyuyoung Kim <[email protected]>
Reviewed-by: Dave Tapuska <[email protected]>
Reviewed-by: Andrey Kosyakov <[email protected]>
Reviewed-by: Matthew Jones <[email protected]>
Reviewed-by: Elly Fong-Jones <[email protected]>
Reviewed-by: Fabrice de Gans-Riberi <[email protected]>
Reviewed-by: Sean Topping <[email protected]>
Reviewed-by: Kentaro Hara <[email protected]>
Reviewed-by: Bo <[email protected]>
Reviewed-by: Kinuko Yasuda <[email protected]>
Cr-Commit-Position: refs/heads/master@{#806042}
diff --git a/content/browser/renderer_host/navigation_controller_impl.cc b/content/browser/renderer_host/navigation_controller_impl.cc
index d4fd1aa..6bdd9cb 100644
--- a/content/browser/renderer_host/navigation_controller_impl.cc
+++ b/content/browser/renderer_host/navigation_controller_impl.cc
@@ -1992,7 +1992,7 @@
     last_committed_url = last_committed->GetURL();
   }
 
-  WebPreferences prefs = rfhi->GetOrCreateWebPreferences();
+  auto prefs = rfhi->GetOrCreateWebPreferences();
   const url::Origin& committed_origin =
       rfhi->frame_tree_node()->current_origin();
   bool is_same_origin = last_committed_url.is_empty() ||