[ios] Fix uses of ios::ChromeBrowserState in /ios/chrome/browser/ui/send_tab_to_self

The ChromeBrowserState has been moved from the "ios" namespace
to the global namespace by http://crrev.com/c/2014913. Fix the
uses from ios::ChromeBrowserState to ChromeBrowserState.

Also remove includes of chrome_browser_state_forward.h and use
a simple forward declaration instead (since the old name is no
longer necessary).

This CL was uploaded by git cl split.

R=jeffreycohen@chromium.org

Bug: 1042208
Change-Id: Ib396345f37691f2b87d6596c5c96ce50ee913442
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2015091
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Jeffrey Cohen <jeffreycohen@chromium.org>
Commit-Queue: Jeffrey Cohen <jeffreycohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#734572}

ios/chrome/browser/ui/send_tab_to_self/send_tab_to_self_coordinator.h

@@ -17,8 +17,7 @@
     NS_UNAVAILABLE;
 // Unavailable, use -initWithBaseViewController:browser:.
 - (instancetype)initWithBaseViewController:(UIViewController*)viewController
-                              browserState:
-                                  (ios::ChromeBrowserState*)browserState
+                              browserState:(ChromeBrowserState*)browserState
     NS_UNAVAILABLE;
 
 @end