[ios clean] Sets Webstate's SetWebUsageEnabled to true on creation.

When creating a new Webstate we hit a DCHECK since SetWebUsageEnabled
is false, this CL fixes that problem by setting the Webstate 
SetWebUsageEnabled to true on creation. 

Bug: 
Change-Id: I0fd5b9d57c9d66d78bc5370d54fe8f38065f5932
Reviewed-on: https://chromium-review.googlesource.com/575841Reviewed-by: Ed Chin <edchin@chromium.org>
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487613}

ios/clean/chrome/browser/ui/tab_grid/tab_grid_coordinator.mm

@@ -178,6 +178,7 @@
       self.browser->browser_state());
   std::unique_ptr<web::WebState> webState =
       web::WebState::Create(webStateCreateParams);
+  webState->SetWebUsageEnabled(true);
   self.webStateList.InsertWebState(self.webStateList.count(),
                                    std::move(webState));
   [self showTabGridTabAtIndex:self.webStateList.count() - 1];